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Amber

By
Mahmut MAT
-

Amber is a fascinating organic gemstone that has captured human fascination for millennia. It’s not a mineral, but rather a fossilized resin from ancient trees. This unique material has played a significant role in various cultures and has been used for both decorative and practical purposes.

Amber is a solidified resin that originated from coniferous trees, primarily in the Pinaceae family, during prehistoric times. Resin is the sticky substance that oozes from trees when they are wounded, serving as a protective mechanism against pests and pathogens. Over time, this resin can become buried and undergo a process of fossilization, transforming into amber.

Amber’s composition is primarily carbon, hydrogen, and oxygen, with traces of sulfur. It’s relatively lightweight and can vary in color from pale yellows and oranges to darker reds and browns. The coloration is influenced by factors such as the type of tree it originated from, the presence of impurities, and the length of time it underwent fossilization.

Formation of Amber:

The journey of amber begins when resin flows from trees as a protective response to injuries. This resin can trap various organic materials, such as insects, plant matter, and even air bubbles. Over time, the resin can fall to the ground, get carried by water, and eventually become buried by sediment. The pressure and heat from geological processes cause the resin to polymerize, gradually solidifying it into amber.

The process of amber formation is a slow one, taking millions of years. During this time, the resin undergoes chemical changes that contribute to its unique properties, including its distinct transparency and ability to hold preserved organisms.

Significance and Historical Uses:

Amber has held cultural and commercial significance for countless societies throughout history. Its captivating appearance, often resembling drops of sunlight trapped within a stone, led many civilizations to attribute it with mystical and protective qualities. Amber was frequently used in jewelry and amulets for adornment and as a symbol of status.

In ancient times, amber was traded along extensive routes, forming part of the fabled Amber Road that connected Northern Europe to the Mediterranean. It was particularly valued by the ancient Greeks and Romans, who associated it with the gods and believed it had healing properties.

Amber’s ability to preserve prehistoric organisms is one of its most remarkable traits. Insects, plants, and even small animals have been found perfectly preserved within amber, providing valuable insights into ancient ecosystems and the evolution of life on Earth.

In more recent times, amber continues to be cherished for its aesthetic and historic value. It’s used in various forms of jewelry, carvings, and decorative art. Additionally, modern science has utilized the fossilized inclusions in amber to study the biology of ancient organisms and gain a better understanding of Earth’s past.

In conclusion, amber is a captivating gemstone that offers a window into the ancient past. Its formation from fossilized tree resin, coupled with its historical significance and uses, makes it a truly unique and cherished material in both cultural and scientific realms.

Geological Formation

The process through which tree resin transforms into amber is a complex one, involving several stages over millions of years. Here’s a detailed breakdown of the formation process:

  1. Resin Exudation: When certain types of trees, particularly conifers in the Pinaceae family, experience injuries or stress, they release resin as a defense mechanism. This resin is a sticky substance that oozes from the tree’s wounds, sealing them and protecting against pests, pathogens, and environmental stressors.
  2. Transport and Accumulation: The resin can flow down the tree’s bark and collect on the ground or other surfaces. Over time, various materials such as insects, plant debris, and air bubbles might get trapped within the sticky resin.
  3. Burial: If the resin isn’t disturbed or degraded, it can become buried by sediment or transported by water, eventually reaching riverbeds, lakes, or coastal areas. Burial prevents the resin from being exposed to air, which helps in preserving its organic components.
  4. Diagenesis: Under the pressure and heat of geological processes, the resin undergoes diagenesis, a series of chemical changes. Polymerization occurs, where the volatile components of the resin evaporate, and the remaining complex organic compounds bond together, forming a solid substance.
  5. Hardening and Fossilization: Over time, the polymerized resin hardens further, and its structure becomes more crystalline. The process of fossilization involves the infiltration of minerals from surrounding sediments, which can contribute to the final color and appearance of the amber.
  6. Tectonic Movements and Uplift: Geological processes such as tectonic movements, erosion, and uplift bring amber deposits closer to the surface. This can expose them to weathering and erosion, allowing them to be discovered by humans.

Factors Influencing Preservation and Transformation:

Several factors influence the preservation and transformation of resin into amber:

  1. Type of Resin: Different tree species produce resins with varying chemical compositions. Some resins are more conducive to amber formation due to their higher levels of polymerizable compounds.
  2. Environmental Conditions: The conditions of the environment where the resin is deposited play a role. Burial in low-oxygen, anaerobic conditions helps prevent decay and decomposition.
  3. Pressure and Temperature: The pressure and temperature experienced by the buried resin influence the speed and extent of its polymerization and hardening.
  4. Mineral Content: The minerals present in the surrounding sediments can infiltrate the resin during fossilization, affecting its appearance and properties.
  5. Time: Amber formation is a slow process, taking millions of years. The longer the resin is buried, the more extensive the polymerization and fossilization processes become.

Geological Time Periods and Major Amber Deposits:

Amber deposits are associated with specific geological time periods, and they offer insights into the ancient environments and ecosystems of those times. Some major amber deposits include:

  1. Baltic Amber (Eocene): The most famous and commercially valuable amber comes from the Baltic region (Northern Europe). The majority of Baltic amber is dated to the Eocene epoch, which spanned from about 56 to 33.9 million years ago.
  2. Dominican Amber (Miocene to Pleistocene): Found in the Dominican Republic and neighboring areas, this amber ranges in age from the Miocene (about 23 to 5.3 million years ago) to the Pleistocene (about 2.6 million to 11,700 years ago).
  3. Mexican Amber (Miocene): Mexican amber is primarily from the mid-Miocene period, around 15 to 23 million years ago, and is found in regions like Chiapas.

These major amber deposits provide windows into diverse ancient ecosystems, offering scientists valuable insights into the flora, fauna, and climatic conditions of the past.

Properties

Physical Properties:

  1. Hardness: Amber ranks around 2 to 3 on the Mohs scale of hardness, which means it is relatively soft compared to other gemstones and can be scratched easily by harder materials.
  2. Density: Amber is relatively lightweight, with a density ranging from 1 to 1.2 g/cm³.
  3. Transparency: Amber is often transparent to translucent, allowing light to pass through it with varying degrees of clarity.
  4. Luster: Amber has a resinous or vitreous luster when polished, giving it a shiny appearance.
  5. Electrostatic Properties: Amber can develop static electricity when rubbed, a phenomenon known as “electrostatic charging.” This property was famously observed by the ancient Greeks, who named it “elektron,” which eventually led to the term “electricity.”

Chemical Properties:

  1. Composition: Amber is primarily composed of carbon, hydrogen, and oxygen, with minor amounts of sulfur. The complex organic compounds in amber result from the polymerization of the original tree resin.
  2. Volatility: Over time, volatile components in the resin evaporate, leaving behind more stable compounds that contribute to amber’s preservation.
  3. Flammability: Amber is flammable and can burn with a smoky, aromatic flame due to its organic composition.

Types of Amber

Amber can be classified into different types based on its origin, characteristics, and geological age. Some notable types include:

  1. Baltic Amber: Originating primarily from the Baltic Sea region (Northern Europe), Baltic amber is one of the most well-known and sought-after types. It’s famous for its rich colors, clarity, and the wide range of preserved inclusions it contains.
  2. Dominican Amber: Found in the Dominican Republic and surrounding areas, Dominican amber is known for its wide array of colors and inclusions. It tends to be more transparent than Baltic amber and can range from pale yellow to deep red.
  3. Succinite: A term often used to refer to Baltic amber due to its scientific name, Succinum. It’s derived from the Latin word for amber, “succinum.”
  4. Burmite: Hailing from Myanmar (Burma), Burmite is amber from the Cretaceous period, known for its ancient inclusions. It can have a wide range of colors and is sometimes cloudy due to its geological age.
  5. Mexican Amber: This amber comes from Mexico, particularly the Chiapas region. It can vary in color from pale yellow to deep red and often contains a diversity of inclusions.

Variations in Color, Transparency, and Inclusions:

Amber displays a captivating range of variations:

  1. Color: Amber can exhibit various colors, including shades of yellow, orange, red, brown, and even rare greens and blues. The color is influenced by factors such as the resin’s original composition, the presence of impurities, and the conditions of fossilization.
  2. Transparency: The transparency of amber can vary widely, from nearly opaque to highly transparent. This impacts how much light passes through the gemstone, affecting its visual appeal.
  3. Inclusions: One of the most remarkable features of amber is the preserved organic inclusions trapped within it. These inclusions can include insects, plant fragments, air bubbles, and even small vertebrates. These trapped relics provide valuable insights into ancient ecosystems and life forms.

In conclusion, amber’s physical and chemical properties, along with its diverse types, colors, transparency levels, and inclusions, make it a truly unique gemstone that offers both aesthetic beauty and scientific significance.

Amber as a Gemstone

Amber holds a special place in the world of gemstones due to its organic origin, unique properties, and historical significance. While not a mineral like many other gemstones, its beauty and the captivating inclusions it can contain make it highly desirable for jewelry and decorative purposes.

Value Factors for Amber as a Gemstone:

The value of amber as a gemstone is influenced by several factors:

  1. Color: Color is a primary determinant of amber’s value. Clear, vibrant, and rich colors, such as deep oranges, reds, and yellows, are highly prized. Rarer colors, like green and blue, are even more valuable.
  2. Clarity: Clarity refers to the degree of transparency and the absence of significant internal flaws or fractures. Clear, transparent amber with minimal internal inclusions commands higher prices.
  3. Size: Larger pieces of amber are generally more valuable, as they provide more material for crafting jewelry and allow the inclusions to be better observed.
  4. Inclusions: While inclusions are often considered flaws in other gemstones, in amber, they can greatly enhance its value. The presence of well-preserved and interesting inclusions, such as insects or plant fragments, adds to the uniqueness and desirability of the gem.
  5. Color Variation: Amber with multiple colors or color zones can be particularly sought after. This “sunburst” effect, where the colors radiate from a central point, can enhance its visual appeal.

Cutting, Polishing, and Jewelry Settings:

The process of crafting amber into jewelry involves several steps:

  1. Cutting: Amber is relatively soft compared to other gemstones, so it can be easily cut and shaped. Skilled artisans cut raw amber pieces into various shapes such as cabochons, beads, pendants, and even intricately carved figurines.
  2. Polishing: After cutting, amber is polished to enhance its luster and translucency. Polishing brings out its natural shine, giving it a smooth and glossy appearance.
  3. Setting: Amber is often set in jewelry using traditional metal settings like sterling silver, gold, or even more contemporary materials. Bezel settings, which encircle the gem with a metal rim, are common for amber jewelry, as they offer protection and highlight the gem’s beauty.
  4. Design: Amber’s warm and earthy tones make it suitable for various jewelry styles, from traditional to modern. It’s used in rings, necklaces, bracelets, earrings, and even more elaborate statement pieces.
  5. Inclusion Display: In jewelry, craftsmen often design settings to showcase amber’s inclusions. Insects or other inclusions trapped within the gem can become central focal points of a piece, creating a unique and storytelling jewelry item.
  6. Enhancements: Amber is typically not treated or enhanced, as its natural beauty and historical significance are its main attractions.

In conclusion, amber’s status as a gemstone is distinguished by its natural origin, captivating inclusions, and historical allure. The value of amber is influenced by color, clarity, size, and the uniqueness of its inclusions. Its versatile use in jewelry and the craftsmanship involved in cutting, polishing, and setting ensure that amber remains a cherished and timeless gemstone choice.

Occurrence and Locations

Amber is found in various regions around the world, with different deposits offering unique qualities and characteristics. Here are some of the notable geographic locations where amber is found:

  1. Baltic Region (Northern Europe): The Baltic Sea area, encompassing countries like Poland, Russia, Lithuania, Latvia, and Estonia, is renowned for its Baltic amber. This amber is primarily from the Eocene epoch and is highly valued for its range of colors, transparency, and the exceptional preservation of inclusions, including insects and plant matter.
  2. Dominican Republic: The Dominican Republic and neighboring Caribbean countries are known for their deposits of Dominican amber. This amber is more diverse in color than Baltic amber and often contains a wide array of inclusions, showcasing ancient ecosystems and flora.
  3. Mexico (Chiapas): The Chiapas region in southern Mexico is a significant source of Mexican amber. This amber can vary in color from pale yellow to deep red and can contain intriguing inclusions. It’s often used in jewelry and artistic carvings.
  4. Myanmar (Burma): Burmite, amber from Myanmar, is of Cretaceous age, making it some of the oldest known amber. It’s known for its ancient inclusions and can be cloudy due to its geological age.
  5. Canada: Amber deposits have also been discovered in Canada, particularly in the province of Alberta. This amber is known for preserving a variety of prehistoric insects and plant matter.
  6. Ukraine: Amber deposits are found in the Rivne region of Ukraine. Ukrainian amber, like Baltic amber, dates back to the Eocene epoch and is valued for its quality and preservation of inclusions.
  7. Italy: The Sicilian amber, found in Italy, dates back to the Miocene epoch and is known for its unique blue color due to the presence of anthracene.
  8. Lebanon: Lebanese amber, also from the Cretaceous period, is another ancient source. It is valued for its well-preserved inclusions and is considered among the oldest ambers.
  9. Indonesia: Amber deposits have been found in Indonesia, including Sumatra and Borneo. Indonesian amber, also known as Borneo amber, is relatively less studied compared to other deposits.
  10. New Zealand: A rare type of amber known as kauri gum is found in New Zealand. Kauri gum is derived from the resin of kauri trees and is valued for its use in jewelry and decorative objects.

These are just a few examples of the geographic locations where amber is found. Each deposit has its own geological history, unique characteristics, and inclusions that provide insights into the ancient world and ecosystems. Amber’s global presence has contributed to its rich cultural, scientific, and commercial significance.

Aragonite

By
Mahmut MAT
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Aragonite crystals. Aragonite is a variant of calcium carbonate, along with the mineral calcite. Calcium carbonate is a very common mineral that occurs naturally in many rocks, such as limestone and chalk. This sample, found in Morocco, is 4 centimetres long.
Aragonite crystals. Aragonite is a variant of calcium carbonate, along with the mineral calcite. This sample, found in Morocco, is 4 centimetres long.
crystals of Aragonite mineral stone isolated on white background

Aragonite is a carbonate mineral and its formula is calcium carbonate. It has the same formula as Calcite and Vaterite, but has a different crystal structure. They are tabular, prismatic or needle-like, often with steep pyramidal or chisel-shaped ends, and can form columnar or spreading aggregates. Multiple twin crystals that appear hexagonal in shape are common. Although aragonite sometimes resembles calcite, it is easily distinguished by the absence of rhombic cleavage. Samples can be white, colorless, gray, yellowish, green, blue, reddish, purple or brown. Aragonite is found in oxidized areas of ore deposits and in evaporites, hot spring deposits and caves. It is also found in some metamorphic and igneous rocks and is formed by biological and physical processes, including precipitation from marine and freshwater environments.

Name: For its first-noted occurrence in the Aragon region, Spain

Association: For its first-noted occurrence in the Aragon region, Spain

Polymorphism & Series: Trimorphous with calcite and vaterite

Mineral Group: Aragonite group

Chemical Properties

FormulaCaCO3
Common ImpuritiesSr,Pb,Zn

Aragonite Physical Properties

Crystal habitOrthorhombic
ColorColorless to white or grey, often stained various hues by impurities, such as blue, green, red or violet; colourless in transmitted light.
StreakUncolored/white.
LusterVitreous, Resinous
CleavageDistinct/Good On {010} distinct; On {110} and {011} very indistinct.
DiaphaneityTransparent, Translucent
Mohs Hardness3½ – 4
TenacityBrittle
Density2.947
FractureSub-Conchoidal

Aragonite Optical Properties

TypeBiaxial (-)
2V:Measured: 18° to 19°, Calculated: 16° to 18°
RI values:nα = 1.529 – 1.530 nβ = 1.680 – 1.682 nγ = 1.685 – 1.686
TwinningSingle crystals are typically twinned cyclically on {110} producing pseudo-hexagonal aggregates of contact and penetration twins. Polysynthetic twinning produces lamellae or fine striations parallel to [100].
Optic SignBiaxial (-)
Birefringenceδ = 0.156
ReliefHigh
Dispersion:weak

Aragonite Occurrence

It turns into calcite over geological time. Primary sediment in warm marine waters such as oolites and carbonate mud, an essential clastic sedimentary component as the hard parts of the shells and skeletons of many marine micro-organisms; also from evaporite deposits; in sinter in hot springs and in stalactite in caves; characteristic of high pressure, low temperature (blueschist facies) metamorphism; as amygdullary in basalt and andesite; It is a secondary component in altered ultramafic rocks.

Aragonite is a high pressure polymorph of calcium carbonate. Therefore, it occurs in high pressure metamorphic rocks such as those formed in subduction zones.

Aragonite is metastable at low pressures near the Earth’s surface and is therefore often replaced by calcite in fossils. Aragonite older than the Carboniferous is essentially unknown. It can also be synthesized by adding a solution of calcium chloride in water-ethanol mixtures at ambient temperatures or to a sodium carbonate solution at temperatures above 60 °C (140 °F).

Uses of Aragonite

Aragonite provides essential materials for marine life and also keeps the pH of the water close to its natural level to prevent the dissolution of biogenic calcium carbonate.

Aragonite has been successfully tested for the removal of contaminants such as zinc, cobalt and lead from contaminated wastewater.

Claims that magnetic water treatment can reduce calcification by converting calcite to aragonite have been met with skepticism, but remain under investigation.

Distribution

Many localities, but fine crystals are uncommon.

  • From Molina, Guadalajara Province, Spain.
  • Fine crystals from Racalmuto, Cianciana, and Agrigento, Sicily, Italy.
  • At Dogn´acska and Spania Dolina (Herrengrund), Slovakia.
  • From Tarnowitz, Silesia, Poland.
  • At ˇ the Erzberg, near Eisenerz, Styria, and from Leogang, Salzburg, Austria.
  • On the Spitzberg, Hoˇrenz, near B´ılina, Czech Republic.
  • From Frizington and Cleator Moor, Cumbria, England.
  • Fine examples at the Touissit mine, near Oujda, and from Tazouta, near Sefrou, Morocco.
  • Large crystals from Tsumeb, Namibia.
  • In the USA, in caves at Bisbee, Cochise Co., Arizona; large crystals from near Lake Arthur, Chavez Co., also near Santa Rosa, Guadalupe Co., New Mexico; in the Passaic mine, Sterling Hill, Ogdensburg, Sussex Co., New Jersey

Pearl

By
Mahmut MAT
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Pearls, often referred to as “gems of the sea,” are unique and exquisite organic gemstones that have captivated humanity for centuries. Their iridescent luster and timeless elegance have made them a symbol of beauty, wealth, and sophistication across cultures. Formed within the depths of certain mollusks, pearls are a result of nature’s meticulous craftsmanship.

Pearls are spherical or irregularly shaped objects formed within the soft tissue of certain mollusks, primarily oysters and mussels. These gemstones are composed of layers of calcium carbonate crystals known as aragonite, along with a protein called conchiolin. The interaction between these elements, along with environmental factors, contributes to the pearl’s unique visual characteristics.

Brief Overview of Pearl Formation

The fascinating process of pearl formation begins when an irritant, such as a grain of sand or a parasite, enters the soft tissues of a mollusk. In response to this intrusion, the mollusk’s defense mechanism is triggered. It secretes layers of nacre, a combination of aragonite and conchiolin, around the irritant. This process continues over time, with successive layers being deposited, creating a luminous and iridescent pearl.

There are two main types of pearls: natural pearls and cultured pearls. Natural pearls form when the irritant enters the mollusk naturally, without any human intervention. Cultured pearls, on the other hand, are formed through a controlled process initiated by humans. In cultured pearl farming, a nucleus made from mussel shell or a mother-of-pearl bead is introduced into the mollusk’s tissue, kickstarting the nacre deposition process.

The factors influencing a pearl’s quality and value include its size, shape, color, luster (the way it reflects light), and surface quality. Pearls can range in color from creamy white to shades of pink, blue, green, and even black. The overall appeal of a pearl is the result of these unique combinations of characteristics.

Pearls have held a significant place in human culture throughout history, symbolizing purity, wisdom, and luxury. From ancient civilizations to modern fashion runways, pearls continue to evoke a sense of elegance and grace, making them a cherished treasure both in the natural world and in the realm of human adornment.

Pearl Formation

Pearls are formed through a natural biological process within certain species of mollusks, primarily oysters and mussels. The process begins when an irritant, such as a grain of sand or a parasite, enters the soft tissue of the mollusk. In response to this foreign object, the mollusk’s defense mechanism is triggered. The mollusk secretes a substance called nacre, also known as mother-of-pearl, which is composed of alternating layers of aragonite (a crystalline form of calcium carbonate) and conchiolin (an organic protein).

Over time, the mollusk continues to deposit layers of nacre onto the irritant. These layers build up and eventually form a pearl. The lustrous surface of the pearl is created by the way light interacts with the layers of nacre, resulting in the characteristic iridescent sheen that pearls are known for.

Natural vs. Cultured Pearls

  1. Natural Pearls: Natural pearls are formed entirely by natural processes without any human intervention. They are quite rare and are the result of a chance occurrence of an irritant entering the mollusk. The process of forming a natural pearl can take several years or even decades, and the outcome is often unpredictable in terms of size, shape, and quality.
  2. Cultured Pearls: Cultured pearls are created through a process that involves human intervention. In pearl farming, a small nucleus, typically a piece of mussel shell or a mother-of-pearl bead, is carefully inserted into the mollusk’s tissue. This irritant serves as a nucleus around which the mollusk deposits layers of nacre, simulating the natural pearl formation process. The controlled environment of pearl farming allows for more predictable results in terms of pearl size, shape, and quality.

Oyster Anatomy and Pearl Formation Process

The anatomy of oysters and other mollusks plays a crucial role in the formation of pearls. Here’s an overview of the process within an oyster:

  1. Mantle Tissue: The mantle is a specialized tissue within the oyster that plays a key role in pearl formation. It secretes both the nacre and the conchiolin, the two main components of pearls.
  2. Irritant Intrusion: When an irritant, such as a grain of sand, enters the oyster’s soft tissue, it becomes lodged between the mantle and the shell. In response to this irritant, the mantle begins to secrete layers of nacre to coat and isolate the irritant.
  3. Nacre Deposition: The oyster continues to deposit layers of nacre onto the irritant over time. This layering process is what creates the pearl’s structure and iridescent appearance.
  4. Pearl Growth: As more layers of nacre are deposited, the pearl grows in size. The size and shape of the pearl are influenced by factors such as the shape of the irritant and the oyster’s unique biology.
  5. Harvesting: In pearl farming, cultured pearls are harvested once they have reached the desired size and quality. The oysters are carefully opened, and the pearls are removed. The oysters can be returned to the water to potentially produce more pearls in the future.

Understanding the intricate relationship between mollusks, their anatomy, and the process of nacre secretion provides insight into the captivating journey that results in the creation of these stunning gemstones.

Types of Pearls

There are several types of pearls, each with its own unique characteristics, colors, and origins. Here’s an overview of some of the most well-known types of pearls:

  1. Freshwater Pearls: These pearls are cultivated in freshwater mussels. They are usually produced in various shapes, including round, oval, and irregular. Freshwater pearls are known for their wide range of colors, from white and pink to lavender and even metallic hues. They are often more affordable compared to other types of pearls.
  2. Akoya Pearls: Akoya pearls are cultured in saltwater oysters, primarily in Japan and China. They are prized for their classic round shape, high luster, and smooth surface. Akoya pearls are traditionally white or cream-colored, with overtones of pink or silver.
  3. South Sea Pearls: These pearls are produced by Pinctada maxima, the largest and rarest species of oysters. South Sea pearls are typically larger in size compared to other pearls, and they are known for their satin-like luster. They come in shades of white, silver, and gold.
  4. Tahitian Pearls: Also known as black pearls, Tahitian pearls are cultured in black-lipped oysters in French Polynesia. Despite their name, they come in a wide range of dark colors, including black, gray, green, and peacock. Their unique colors and overtones make them highly sought after.
  5. Baroque Pearls: Baroque pearls have irregular, non-symmetrical shapes, which can vary from coin-shaped to elongated or abstract forms. They come in both freshwater and saltwater varieties and are often used in creative and artistic jewelry designs.
  6. Keshi Pearls: Keshi pearls are non-nucleated pearls, meaning they form without a nucleus in the pearl sac. They can be found in both saltwater and freshwater mollusks. Keshi pearls are typically small and come in various shapes and colors. They are known for their natural and organic appearance.
  7. Mabe Pearls: Also called blister pearls, mabe pearls are cultivated by attaching a nucleus to the inner shell of an oyster rather than embedding it within the soft tissue. This results in a flat-backed pearl that is often used in earrings, pendants, and rings.
  8. Biwa Pearls: Historically, Biwa pearls referred to freshwater pearls produced in Lake Biwa in Japan. While the original Biwa pearls are no longer produced due to environmental changes, the term is still used to describe certain high-quality freshwater pearls.
  9. Fireball Pearls: These pearls, often found in the South Sea and Tahitian varieties, are characterized by their intense and vibrant colors. The term “fireball” refers to their brilliant and fiery appearance.

These are just a few examples of the diverse types of pearls that exist. Each type has its own unique appeal, making pearls a versatile and captivating choice for jewelry and adornment.

Pearl Jewelry

Pearl jewelry has been treasured for its timeless beauty and elegance for centuries. From classic pearl strands to modern and innovative designs, pearls are used in various forms to create stunning jewelry pieces. Here are some popular types of pearl jewelry:

  1. Pearl Necklaces: Pearl necklaces are perhaps the most iconic and traditional use of pearls in jewelry. They come in different lengths and styles, such as choker, princess, matinee, and opera lengths. A single strand of pearls, often with a simple clasp, is a staple in many jewelry collections.
  2. Pearl Earrings: Pearl earrings are available in various styles, including studs, dangles, and hoops. They can feature different pearl types, sizes, and colors, allowing for versatility in matching different outfits and occasions.
  3. Pearl Bracelets: Pearl bracelets add a touch of sophistication to the wrist. They can be made from various pearl types and strung on silk, wire, or elastic cord. Some designs incorporate multiple strands of pearls or combine pearls with other gemstones.
  4. Pearl Rings: Pearl rings can be both elegant and contemporary. They come in solitaire designs, clusters, and settings that incorporate diamonds or other gemstones. Pearl engagement rings are also becoming a unique choice for those seeking an alternative to traditional diamond rings.
  5. Pearl Pendants: Pearl pendants feature a single pearl or a cluster of pearls suspended from a chain. They can be simple and minimalist or elaborate and ornate, depending on the design.
  6. Pearl Brooches: Pearl brooches add a touch of vintage charm and sophistication to clothing. They can feature pearls of various sizes and styles, often combined with other decorative elements.
  7. Pearl Tiara and Hair Accessories: Pearls are used to create delicate tiaras, hairpins, and combs for special occasions like weddings and formal events. These accessories add a touch of elegance to hairstyles.
  8. Pearl Statement Pieces: Contemporary jewelry designers often create unique and artistic statement pieces using pearls. These can include asymmetrical designs, mixed-media combinations, and avant-garde concepts that showcase pearls in unconventional ways.
  9. Pearl Body Jewelry: Pearls can also be incorporated into body jewelry such as belly button rings, anklets, and toe rings, adding a touch of refinement to body adornment.
  10. Matching Sets: Many jewelry sets include coordinated pieces like necklaces, earrings, and bracelets that feature matching pearls, creating a harmonious look.

Pearls are versatile and can be combined with various metals, gemstones, and materials to create pieces that range from traditional to contemporary. Whether you’re looking for a timeless and elegant piece or a bold and innovative design, pearl jewelry offers a wide range of options to suit different styles and preferences.

Famous Pearls

La Peregrina Pearl

Several famous pearls have gained worldwide recognition due to their size, color, history, and the stories behind them. Here are a few examples of famous pearls:

  1. La Peregrina Pearl: One of the most famous pearls in history, La Peregrina, was discovered in the 16th century off the coast of Panama. Its name means “The Pilgrim” in Spanish. The pearl’s unique pear shape and size (approximately 50.56 carats) have made it a coveted gem for centuries. It has passed through the hands of various monarchs and celebrities, including Queen Mary I of England and Richard Burton, who famously gifted it to Elizabeth Taylor as a Valentine’s Day present.
  2. Hope Pearl: The Hope Pearl is a large, natural pearl that measures around 1.7 inches in length. It was once part of the collection of Henry Philip Hope, a gem collector in the early 19th century. The pearl has a remarkable blue-gray color and is often displayed alongside the Hope Diamond in museums due to their similar names and historical connections.
  3. La Regente Pearl: Also known as the “Regent Pearl,” this perfectly symmetrical, white, and nearly round pearl weighs around 140.5 grains (about 35 carats). It was discovered in the Gulf of Panama in the 16th century. The pearl got its name from the French Regent, Philippe II, Duke of Orleans, who owned it in the 18th century.
  4. The Queen’s Pearls: Queen Mary II of England possessed an extensive collection of pearls, including a five-strand pearl necklace. The necklace, which has become iconic, was featured in many of her portraits. The Queen’s Pearls have remained a symbol of royal elegance and sophistication.
  5. Arco Valley Pearl: Discovered in 1982, the Arco Valley Pearl is one of the largest freshwater pearls ever found. It weighs approximately 575 carats and measures over 2 inches in diameter. Its unusual size and shape have contributed to its fame.
  6. Peregrina Pearl (Revisited): In addition to the historic La Peregrina Pearl, a replica of the original was created in 2011. This replica, known as “La Peregrina II,” was made using a silicone mold of the original pearl. It was commissioned by Elizabeth Taylor’s estate after the original pearl was sold at auction.
  7. Ducal Pearl Necklace: This necklace, part of the British royal jewelry collection, features a large baroque pearl pendant suspended from a diamond necklace. The pearl is believed to have belonged to Queen Mary I of England and was passed down through generations.

These famous pearls have captured the imagination of people around the world and continue to be admired for their beauty, history, and the stories they tell.

Physical Properties

Pearls are not only prized for their beauty but also for their unique physical properties. Here are some key physical properties of pearls:

  1. Luster: Luster refers to the way light interacts with the surface of a pearl. Pearls are known for their exquisite luster, which gives them a soft, glowing appearance. The iridescence comes from the overlapping layers of nacre, which refract and reflect light, creating a shimmering effect.
  2. Color: Pearls come in a wide range of colors, from classic white and cream to shades of pink, lavender, gray, black, and even rare and exotic colors like golden and peacock. The color of a pearl is influenced by the type of mollusk, the water it’s cultivated in, and other environmental factors.
  3. Size: Pearls can vary greatly in size, from tiny seed pearls to larger pearls that are several centimeters in diameter. The size of a pearl is determined by factors such as the size of the irritant, the mollusk’s biology, and the length of time the pearl is allowed to grow.
  4. Shape: Pearls come in various shapes, including round, oval, button, drop, baroque (irregular), and circled (with rings around the surface). The round shape is particularly prized and considered the classic pearl shape.
  5. Surface Quality: The surface of a pearl can have various imperfections, including blemishes, spots, and irregularities. Pearls with smoother surfaces are typically more valuable. However, some types of pearls, such as baroque pearls, embrace their unique surface characteristics.
  6. Nacre Thickness: The thickness of the nacre layers is a crucial factor in determining the quality and durability of a pearl. Thicker nacre generally leads to stronger pearls with better luster.
  7. Density and Hardness: Pearls are relatively soft compared to other gemstones, with a hardness of 2.5 to 4.5 on the Mohs scale. This makes them more susceptible to scratches and damage. Their density varies depending on the type of pearl.
  8. Translucency: High-quality pearls often have a degree of translucency, allowing some light to pass through the layers of nacre. This property contributes to the pearl’s overall radiance.
  9. Weight: The weight of a pearl is typically measured in carats (the same unit used for diamonds and other gemstones). The weight is influenced by the pearl’s size, density, and type.
  10. Fluorescence: Some pearls may exhibit fluorescence under certain lighting conditions. This can add a unique dimension to their appearance, especially in pearls with darker colors.

Understanding these physical properties can help both consumers and collectors appreciate the distinctiveness and value of different types of pearls. The interplay of these properties contributes to the allure and charm of pearls as treasured gemstones.

Occurrence

Pearls are formed naturally within certain species of mollusks, including oysters and mussels. The occurrence of pearls involves specific conditions and factors that contribute to their formation. Here’s an overview of how pearls occur:

  1. Mollusk Habitat: Mollusks that produce pearls inhabit various aquatic environments, including oceans, seas, rivers, and freshwater bodies. Different types of mollusks thrive in different habitats, and the conditions of their environment play a significant role in pearl formation.
  2. Irritant Intrusion: The pearl formation process begins when an irritant, such as a grain of sand, a parasite, or another foreign object, enters the soft tissue of a mollusk. This irritant becomes lodged within the mantle tissue of the mollusk.
  3. Nacre Secretion: In response to the irritant, the mollusk’s mantle tissue starts secreting nacre, a combination of aragonite (calcium carbonate) and conchiolin (an organic protein). The nacre is gradually deposited in layers around the irritant. This layering process is what ultimately forms the pearl.
  4. Layering Over Time: Over time, the mollusk continues to deposit layers of nacre onto the irritant. These layers build up, gradually forming the pearl’s size and shape. The time required for a pearl to form can vary greatly, ranging from several months to several years.
  5. Natural and Cultured Pearls: Pearls can occur naturally when the irritant enters the mollusk without human intervention. These are referred to as natural pearls and are quite rare. In contrast, cultured pearls are formed through a controlled process initiated by humans. In pearl farming, a nucleus is intentionally introduced into the mollusk’s tissue to stimulate nacre deposition.
  6. Pearl Types and Locations: Different types of pearls are associated with specific mollusk species and geographic regions. For example, Akoya pearls are primarily cultivated in Japan and China, while South Sea pearls are found in the waters of the South Pacific. Freshwater pearls are cultivated in various freshwater bodies around the world.
  7. Environmental Factors: The quality and characteristics of pearls are influenced by environmental factors such as water temperature, water quality, and the mollusk’s diet. These factors affect the growth rate, size, color, and luster of the pearls.
  8. Harvesting: In the case of cultured pearls, once the pearls have reached the desired size and quality, they are harvested by carefully opening the mollusks. The pearls are then removed, and the mollusks can be returned to the water to potentially produce more pearls in the future.

Overall, the occurrence of pearls is a fascinating natural process that involves the intricate interaction between mollusks, their environment, and the specific conditions that lead to the formation of these exquisite gemstones.

Pearl Types and Locations

Pearls come in various types, each associated with specific mollusk species and geographic regions. Different types of pearls are cultivated in various parts of the world, and their unique characteristics make them highly valued in the world of jewelry and adornment. Here’s a breakdown of some pearl types and their locations:

  1. Akoya Pearls:
    • Type: Saltwater pearl
    • Location: Primarily cultivated in Japan and China, with Japanese Akoya pearls being particularly renowned. They are also produced in other regions with suitable conditions.
    • Characteristics: Known for their classic round shape, high luster, and smooth surface. They are often white or cream-colored, with overtones of pink or silver.
  2. South Sea Pearls:
    • Type: Saltwater pearl
    • Location: Cultivated in the warm waters of the South Pacific, including countries like Australia, Indonesia, the Philippines, and Myanmar (Burma).
    • Characteristics: Larger in size compared to other pearls, with a satin-like luster. They come in shades of white, silver, and gold.
  3. Tahitian Pearls:
    • Type: Saltwater pearl
    • Location: Cultured in black-lipped oysters primarily in French Polynesia, including the islands of Tahiti.
    • Characteristics: Known for their unique dark colors, ranging from black and gray to green, peacock, and iridescent overtones.
  4. Freshwater Pearls:
    • Type: Freshwater pearl
    • Location: Cultivated in various freshwater bodies, including lakes, rivers, and ponds, around the world. China is a major producer of freshwater pearls.
    • Characteristics: Come in various shapes, sizes, and colors, including white, pink, lavender, and metallic hues. Often more affordable than saltwater pearls.
  5. Biwa Pearls:
    • Type: Freshwater pearl
    • Location: Originally cultivated in Lake Biwa in Japan. While the original Biwa pearls are no longer produced due to environmental changes, the term is still used to describe certain high-quality freshwater pearls.
  6. Mabe Pearls:
    • Type: Saltwater or freshwater pearl (depending on origin)
    • Location: Cultivated in various regions, including Japan, Indonesia, and Australia.
    • Characteristics: These pearls are blister pearls, often flat on one side due to their attachment to the shell. They are used in jewelry pieces like earrings and pendants.
  7. Keshi Pearls:
    • Type: Can be either saltwater or freshwater pearls (depending on origin)
    • Location: Cultivated in both saltwater and freshwater mollusks.
    • Characteristics: Small, irregularly shaped pearls that form without a nucleus. They come in various colors and are often used in artistic and creative jewelry designs.

These are just a few examples of the many pearl types found around the world. Each type has its own distinct characteristics and beauty, making pearls a diverse and captivating choice for jewelry enthusiasts and collectors.

Coral

By
Mahmut MAT
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Coral Rock
Coral Rock
red coral mineral

Coral is a marine animal that belongs to the class Anthozoa and the phylum Cnidaria. It is composed of small, soft-bodied animals called polyps that secrete a hard, calcium carbonate skeleton. Coral is found in warm, shallow waters around the world, and is known for its bright, vibrant colors and unique patterns. While coral is not considered a mineral, it has been used for decorative and ornamental purposes for centuries, and is often classified as a precious or semi-precious gemstone. Coral jewelry and ornaments are popular in many cultures, and are often associated with good luck, protection, and healing properties. However, the harvesting of coral for commercial purposes has had a significant impact on coral populations around the world, and many species are now considered endangered or threatened due to overexploitation and habitat loss.

According to Greek legends, coral is the blood spilled by the hero Perseus when he cut off the head of the monster Medusa. In fact, coral is skeletal material produced by marine animals. Coral is organic and created by living organisms. When coral polyps die, the hardened skeleton remains and this material is used as a gemstone. Most corals are white, but nature can create coral in many other colors, including the popular orange to red forms. Usually its compound is calcium carbonate. Corals have a dull appearance when collected and are then polished. Precious corals, which are red and pink in color, are found around Japan and Malaysia in African coastal waters and the Mediterranean. Black corals are mined from around the West Indies, Australia and Pacific Islands.

Coral is a gemstone that has been used for thousands of years. Besides the beautiful solid colors found in Coral, there may also be color zones or swirls where white, pink, orange and red are most common.

Coral gemstones can be solid or porous depending on polyp formation. Despite Coral’s beautiful colors, it is very soft and brittle and does not make a durable gemstone. It is prone to both scratching and chipping.

Mineral Group: Organic Minerals

Mineralogy: Mostly calcium carbonate (CaCO3)

Environment: Corals are primitive animals belonging to the Phylum Coelenterata or Cnidaria and are found anywhere in the world’s ocean at depths ranging from the tidal mark to the abyss, up to 6000 m.

Coral Varieties

  • Black Coral: Black colored marine coral species from the Antipatharia family.
  • Precious Coral: Also known as Red Coral. Precious Coral has a natural pink to red color and is Coral’s most desirable form of jewellery.
  • Red Coral: The marine coral species corallium rubrum (or several related species) with a natural color from light pink to deep red.

Geological formation of coral

Coral is formed by small animals known as coral polyps, which belong to the class Anthozoa of the phylum Cnidaria. These tiny organisms secrete a hard, calcareous skeleton made of calcium carbonate that serves as their protective home. Over time, as individual polyps die and new ones take their place, the calcareous skeleton grows and forms large, complex structures known as coral reefs.

Coral reefs are typically found in warm, shallow waters in tropical and subtropical regions around the world. They are formed by the accumulation of coral skeletons and other calcareous material over many thousands of years. The growth rate of coral reefs can vary depending on environmental factors such as water temperature, water quality, and the availability of nutrients.

Coral reefs play an important role in the marine ecosystem, providing habitat and shelter for a wide variety of marine life, including fish, crustaceans, and other invertebrates. They also protect coastlines from erosion and storm damage, and are a popular destination for tourism and recreation. However, coral reefs are under threat from a range of factors, including climate change, pollution, overfishing, and habitat destruction.

Coral reefs and their importance

Coral reefs are incredibly important ecosystems that support a vast array of marine life, including fish, invertebrates, and other organisms. They also provide a range of valuable ecological services, such as shoreline protection, nutrient cycling, and carbon sequestration. Here are some of the key reasons why coral reefs are important:

  1. Biodiversity: Coral reefs are one of the most diverse ecosystems on Earth, supporting an estimated 25% of all marine species, despite covering less than 1% of the ocean floor. Many of these species are dependent on coral reefs for their survival, including commercially important fish and shellfish.
  2. Fisheries: Coral reefs provide a critical source of food and income for millions of people around the world. They support some of the world’s most important fisheries, including those for tuna, snapper, and grouper, as well as for many types of shellfish.
  3. Coastal protection: Coral reefs act as natural breakwaters, protecting coastlines from storm surges, waves, and erosion. This is particularly important in areas where sea level rise and increased storm frequency and intensity due to climate change are becoming more common.
  4. Tourism: Coral reefs are a major attraction for tourists, generating billions of dollars in revenue each year. They are particularly popular for activities such as snorkeling and scuba diving, and their beauty and diversity are a major draw for travelers.
  5. Climate regulation: Coral reefs play an important role in regulating the Earth’s climate by absorbing and storing large amounts of carbon dioxide from the atmosphere. This helps to mitigate the impacts of climate change and ocean acidification.

Overall, coral reefs are a vital part of the marine ecosystem and provide a wide range of benefits to human societies. Protecting and preserving these ecosystems is essential for the health and well-being of both marine and human communities around the world.

Physical Properties

Coral is a marine organism that belongs to the family of Anthozoa, and it has certain physical properties that distinguish it from other gemstones. Here are some of the physical properties of coral:

  1. Hardness: Coral has a hardness of 3.5 on the Mohs scale, which makes it relatively soft compared to other gemstones. As a result, it can be easily scratched or damaged, and it requires special care when cleaning or handling.
  2. Density: The density of coral ranges from 1.5 to 1.7 g/cm³, which makes it fairly lightweight compared to other gemstones. This makes it comfortable to wear as jewelry, but it also makes it susceptible to damage from impacts or pressure.
  3. Color: Coral can come in a wide range of colors, including white, pink, red, orange, and black. The color of coral is determined by the presence of pigments and other organic compounds, as well as by the species of coral from which it is derived.
  4. Luster: Coral has a dull to waxy luster, which is characteristic of organic materials. This is different from the glassy or metallic luster of many other gemstones.
  5. Transparency: Coral is opaque, which means that light cannot pass through it. This is because it is made up of numerous small calcium carbonate structures called polyps, which are densely packed together.
  6. Refractive index: The refractive index of coral ranges from 1.486 to 1.658, depending on the species and color of the coral. This determines how light is bent and reflected within the gemstone, and can affect its appearance and beauty.

Overall, coral is a unique and beautiful gemstone that has its own distinct physical properties. Its softness and susceptibility to damage make it important to handle with care, but its beauty and cultural significance make it a popular choice for jewelry and decorative objects.

Uses of coral

Coral has been used for a wide range of purposes throughout human history, from decorative objects to medicinal remedies. Here are some of the most common uses of coral:

  1. Jewelry: Coral is a popular choice for jewelry, particularly in traditional and ethnic designs. It is often carved into beads, pendants, and other shapes, and can be combined with other gemstones and metals to create unique pieces.
  2. Decorative objects: Coral has long been used to create decorative objects, such as sculptures, figurines, and ornaments. Its unique color and texture make it a popular choice for home decor and other decorative applications.
  3. Feng shui: In the practice of feng shui, coral is believed to bring positive energy and luck into the home. It is often used in decor and jewelry to promote good fortune and prosperity.
  4. Aquariums: Coral is also a popular choice for aquarium enthusiasts, as it can provide a natural and beautiful habitat for fish and other marine life.

It is worth noting that the use of coral for decorative purposes has led to overharvesting and damage to coral reefs. As such, it is important to ensure that any coral products you purchase are sustainably sourced and do not contribute to further harm to these fragile ecosystems.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Gem notes: Gemstone Information. Fire Mountain Gems and Beads. (n.d.). Retrieved October 24, 2021, from https://www.firemountaingems.com/resources/encyclobeadia/gem-notes/gmstnprprtscrl1.
  • Minerals.net. 2021. Coral: The gemstone coral information and pictures. [online] Available at: <https://www.minerals.net/gemstone/coral_gemstone.aspx> [Accessed 24 October 2021].

The Cetina River Eye

By
Mahmut MAT
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This reservoir like eye is the source of the Cetina river in southern Croatia. It has a length of 101 km and also its basin covers an area of 1,463 km2. From its source, Cetina descends from an elevation of 385 metres above sea level to the Adriatic Sea. It is the most water-rich river in Dalmatia.

Map of the Catine River

The eye of Cetina river in Croatia is more than 150 meters (490 feet) deep.

The eye of catine river

The source of the river is a karst spring.
Besides the Vismur basin, Cetina also receives a lot of water from the western Bosnian karst field via underground routes. Its lower route starts 20 kilometers (12 mi) from Omiš, near the village of Zadvarje, at an altitude of 49 meters (161 ft) above sea level from the Gubavica Waterfalls. Here it leaves its canyon and flows into a valley that still retains the appearance of a canyon.

The second part of Cetina and its relatively large drop in height was used to build several important hydroelectric power stations.

The total drainage area is around 12,000 km2 and the annual discharge is around 105 m3s-1 as a result of an average annual precipitation of 1380 mm.

Source-of-cetina-river-eye

Cetina River Canyon is also known as an important historical and archaeological site. Archaeologists have found axes from ancient times, the remains of weapons of Roman legionnaires, medieval tools, etc., around the river and in the bed of Cetina. they found it. The finds were items of historical importance.

Catine river source spring
cetina river karst spring

Kaolinite

By
Mahmut MAT
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Kaolinite Mineral Rock
Kaolinite sample from Twiggs County, Georgia, USA. This sample is from the Cretaceous rocks of Georgia

Kaolinite is a clay mineral with chemical composition Al2Si2O5(OH)4. It is an important industrial mineral. Rocks rich in kaolinite are called kaolin. Kaolinite, common group of clay minerals that are hydrated aluminum silicates; they contain the main components of kaolin (china clay). The group includes kaolinite, which is chemically similar but amorphous to kaolinite, and its rarer forms, stalagmite and nacrite, halloysite and allophane.

It is a layered silicate mineral with a tetrahedral silica layer (SiO4) bonded to an octahedral layer of alumina (AlO6) octahedra through oxygen atoms.

Kaolinite, nacrite, and dickite occur as compact or granular masses and mica-like clumps as small, sometimes elongated, hexagonal plates. Feldspars are natural change products of feldspathoids and other silicates. Anoxide, previously considered a kaolinite group mineral with a higher-than-normal silica-to-alumina ratio, is now considered kaolinite and free silica (mainly non-crystalline). For chemical formula and detailed physical properties

Kaolinite is the raw material of brick, pottery and tile.It has played a vital role in the development of human civilization.The most important of these minerals is kaolinite. Kaolinite It forms white, microscopic, pseudo-hexagonal plates.

compact or granular masses and mica-like clumps. Three other minerals – stalagmite, nacrite and halloysite – chemically identical to kaolinite, but monoclinic system. Four found together and often visually indistinguishable.

Kaolinite is a natural product of mica degradation. plagioclase and sodium-potassium feldspars under Effect of water, dissolved carbon dioxide and organic matter acids. Used in agriculture; as a filler in foods such as chocolate; mixed with pectin as an antidiarrheal; as paint expander; as a reinforcing agent in rubber; and as powder agent in foundry operations

Name: The name kaolin is derived from Gaoling. Chinese village near Jingdezhen in southeastern China’s Jiangxi Province. The name entered English in 1727 from the French version of the word: kaolin.

Kaolinite has low shrinkage-swelling capacity and low cation exchange capacity (1–15 meq/100 g). A soft, earthy, usually white mineral (dioctahedral phyllosilicate clay) produced by chemical weathering of aluminum silicate minerals such as feldspar. In many parts of the world it is pink-orange-red with iron oxide, giving it a distinctive rust color. Lighter concentrations give white, yellow or light orange colors. Alternating layers are sometimes found, as in Providence Canyon State Park in Georgia, United States. Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodles or liquid slurry.

Association: Quartz, feldspar, muscovite.

Polymorphism & Series: Dickite, halloysite, and nacrite are polymorphs

Mineral Group: Kaolinite-serpentine group.

Cell Data: Space Group: P1: a = 5.15 b = 8.95 c = 7.39 ® = 91:8 ± ¯ = 104:5 ±¡105:0 ± ° = 90 ± Z = [2]

X-ray Powder Pattern: Scalby, Yorkshire, England (1A). 7.16 (vvs), 3.573 (vvs), 4.336 (vs), 2.491 (s), 2.289 (s), 2.558 (ms), 2.379 (ms)

Chemical Properties

Chemical ClassificationPhyllosilicates Kaolinite-serpentine group
FormulaAl2Si2O5(OH)4
Common ImpuritiesFe,Mg,Na,K,Ti,Ca,H2O

Kaolinite structure showing interlayer hydrogen bonds

Compared to other clay minerals, kaolinite is chemically and structurally simple. It is defined as a 1:1 or TO clay mineral because its crystals consist of stacked layers of RO. Each TO layer consists of a tetrahedral (T) sheet of silicon and oxygen ions bonded to an octahedral (O) sheet of oxygen, aluminum, and hydroxyl ions. The T layer is so named because each silicon ion is surrounded by four oxygen ions forming a tetrahedron. The O layer is so named because each aluminum ion is surrounded by six oxygen or hydroxyl ions arranged at the corners of an octahedron. The two layers in each layer are strongly bonded to each other via shared oxygen ions, while the layers are bonded via hydrogen bonding between the oxygen on the outer face of the T layer of one layer and the hydroxyl on the outer face of the O layer of the next layer.

Structural Transformations

Kaolinite group clays undergo a series of phase transformations after heat treatment in air at atmospheric pressure.

Milling

Grinding kaolinite results in the formation of a mechanochemically amorphous phase similar to metakaolin, although the properties of this solid are quite different. Great energy is required to convert kaolinite into metakaolin.

Drying

Below 100 °C (212 °F), exposure to dry air will slowly remove liquid water from the kaolin. The final state of this transformation is called “skin dryness”. Between 100 °C and about 550 °C (1,022 °F), the remaining liquid water is expelled from the kaolinite. The final state of this transformation is called “bone dryness”. Over this temperature range, the removal of water is reversible: if kaolin is exposed to liquid water, it will be reabsorbed and decomposed into fine particle form. Subsequent transformations represent irreversible and permanent chemical changes.

Metakaolin

Endothermic dehydration of kaolinite begins at 550-600 °C and produces disordered metakaolin, but continuous loss of hydroxyl is observed up to 900 °C (1,650 °F). Although historically there has been much disagreement about the nature of the metakaolin phase, extensive research has led to general consensus that metakaolin is not a simple mixture of amorphous silica (SiO2) and alumina (Al2O3), but rather a complex amorphous structure that retains some of it. longer range order (but certainly not crystalline) due to stacking of hexagonal layers.

Physical Properties

Crystal habit 
ColourWhite to cream and pale-yellow, also often stained various hues, tans and browns being common.
StreakWhite, or paler than the sample.
Hardness2 – 2½
LusterWaxy, Pearly, Dull, Earthy
CleavagePerfect on {001}.
DiaphaneityTranslucent, Opaque
Crystal SystemTriclinic
TenacityFlexible but inelastic
Density2.63 g/cm3 (Calculated)
FractureIrregular/Uneven, Conchoidal, Sub-Conchoidal, Micaceous

Optical Properties

TypeBiaxial (-)
Color / PleochroismTransparent to translucent as single crystals
2V:Measured: 24° to 50°, Calculated: 44°
RI values:nα = 1.553 – 1.563 nβ = 1.559 – 1.569 nγ = 1.560 – 1.570
Birefringence0.017
ReliefLow
Dispersion:none

Occurrence

It replaces other aluminosilicate minerals during hydrothermal alteration and weathering. A common component from which the clay-size fraction of sediments can form by direct precipitation

Kaolinite is one of the most common minerals; As kaolin, it is mined in Malaysia, Pakistan, Vietnam, Brazil, Bulgaria, Bangladesh, France, United Kingdom, Iran, Germany, India, Australia, South Korea, People’s Republic of China, Czech Republic, Spain, South. Africa, Tanzania and the United States.

Kaolinitic saprolite mantles are common in Western and Northern Europe. The ages of these mantles are from Mesozoic to Early Cenozoic.

Kaolinite clay is abundant in soils formed by chemical erosion of rocks in hot and humid climates, such as tropical rainforests. When comparing soils along a slope towards increasingly cooler or drier climates, the proportion of kaolinite decreases while the proportion of other clay minerals such as illite (in colder climates) or smectite (in drier climates) increases. Such climatically relevant differences in clay mineral content are often used to reveal changes in climates in the geological past, where ancient soils were buried and preserved.

Uses Area

  • The main use of the mineral kaolinite (about 50% of the time) is in paper production; Its use provides shine on some coated paper types.
    • in ceramics (main component of porcelain)
    • in toothpaste
    • as a light-emitting material in white incandescent bulbs
    • in cosmetics
    • In industrial insulation material called Kaowool (a type of mineral wool)
    • in ‘pre-work’ skin protection and barrier creams
    • in paint to prolong titanium dioxide white pigment and change gloss levels
    • to change the properties of rubber upon vulcanization
    • in adhesives to change the rheology
    • as a spray applied to crops to prevent insect damage in organic farming and to prevent sunburn on apples
  • As a whitewash in traditional stone-walled houses in Nepal (most common method is to paint the top with white kaolin clay and the middle with red clay; the red clay can extend to the bottom or the bottom can be painted black)
  • As a filler or as a coating to improve the surface in papermaking, as a filler in Edison Diamond Discs Because kaolinite may contain very small traces of uranium and thorium, as an indicator in radiological dating, it was common to treat stomach upset (more recently, industrially produced preparations of kaolinite for the treatment of diarrhea), similar to what parrots (and later humans) originally used in South America.
  • for face masks or soap (known as “White Clay”) body wraps, spa body treatments like cocoons or just spot treatments like feet, back or hands. Essential oil can be added to add a pleasant aroma, or seaweed can be added to increase the nutritional values ​​of the treat.
  • as an adsorbent in water and wastewater treatment to promote blood coagulation in diagnostic procedures, e.g. Kaolin clotting time
  • in the form of metakaolin modified as a pozzolan; When added to a concrete mix, metakaolin accelerates the hydration of Portland cement and takes part in the pozzolanic reaction with portlandite, which is formed in the hydration of the main cement minerals (e.g. alite).
  • in the form of modified metakaolin as a basic ingredient for geopolymer compounds

Safety

People can be exposed to kaolin in the workplace by breathing in the powder or from skin or eye contact.

The Occupational Safety and Health

The Occupational Safety and Health Administration (OSHA) has set the statutory limit (permissible exposure limit) for workplace kaolin exposure as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure in an 8-hour workday. The National Institute of Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) as 10 mg/m3 total exposure TWA 5 mg/m3 respiratory exposure during an 8-hour workday.

Geotechnical engineering

Araştırma sonuçları, kaolinitin jeoteknik mühendisliğinde kullanımının alternatif olarak, özellikle mevcudiyeti toplam kaya kütlesinin %10,8’inden az ise, daha güvenli illit ile değiştirilebileceğini göstermektedir.

Distribution

Pure material from many localities, including:

  • at Kauling, Kiangsi Province,China.
  • In numerous china-clay pits in Cornwall and Devon, England.
  • At Limoges, Haute-Vienne,France.
  • Near Dresden, Kemmlitz, and Zettlitz, Saxony, and elsewhere in Germany.
  • Large deposits in the Donets Basin, Ukraine.
  • In the USA, at Macon, Bibb Co., Georgia; at the Dixie Clay Company mine, and in the Lamar Pit, near Bath, Aikin Co., South Carolina; near Webster, Jackson Co., North Carolina; near Murfreesboro, Pike Co., and at Greenwood, Sebastian Co., Arkansas; from Mesa Alta, Rio Arriba Co., New Mexico.
  • At Huberdeau, Quebec, and near Walton, Nova Scotia, Canada

References

  • Britannica, T. Editors of Encyclopaedia (2018, January 25). Kaolinite. Encyclopedia Britannica. https://www.britannica.com/science/kaolinite
  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
  • Smith.edu. (2019). Geosciences | Smith College. [online] Available at: https://www.smith.edu/academics/geosciences [Accessed 15 Mar. 2019].

Economically Important Metal Concentrations in Earth’s Crust

By
Mahmut MAT
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Economically Important MetalConcentrations in Earth’s Crust
Economically Important MetalConcentrations in Earth’s Crust

The Earth’s crust contains a wide range of metal concentrations, but not all of them are economically viable for extraction. The economic viability of metal concentrations in the Earth’s crust depends on several factors, including the abundance of the metal, its concentration in ores or minerals, the accessibility and cost of extraction, and the demand and market price for the metal. Here are some examples of economically important metal concentrations in the Earth’s crust:

Economically Important Metal
  1. Aluminum (Al): Aluminum is the most abundant metal in the Earth’s crust, comprising about 8% of the crust by weight. It is widely used in various industrial applications, including transportation, construction, packaging, and electrical transmission. Bauxite, a type of laterite deposit, is the main source of aluminum, with major deposits found in countries like Australia, Guinea, and Brazil.
  2. Iron (Fe): Iron is a crucial metal used in the production of steel, which is used in infrastructure, machinery, and many other applications. Iron is abundant in the Earth’s crust, comprising about 5% of the crust by weight. Iron ore deposits are found in various forms, including hematite, magnetite, and taconite, with major deposits found in countries like Australia, Brazil, and China.
  3. Copper (Cu): Copper is an essential metal used in various industries, including electrical wiring, plumbing, and electronics. Copper deposits can be found in a variety of geological settings, including porphyry deposits, sedimentary deposits, and volcanic-hosted massive sulfide deposits. Major copper deposits are found in countries like Chile, Peru, and the United States.
  4. Gold (Au): Gold is a precious metal used in jewelry, electronics, and investment, and has been valued for its rarity and beauty for thousands of years. Gold deposits can occur in a variety of forms, including placer deposits, lode deposits, and epithermal deposits. Major gold-producing countries include China, Australia, and Russia.
  5. Nickel (Ni): Nickel is a key metal used in the production of stainless steel, batteries, and other industrial applications. Nickel deposits can be found in various geological settings, including laterite deposits, sulfide deposits, and magmatic deposits. Major nickel deposits are found in countries like Indonesia, Russia, and Canada.
  6. Zinc (Zn): Zinc is an important metal used in the production of galvanized steel, batteries, and other applications. Zinc deposits are typically found in sedimentary-hosted deposits, such as carbonate-hosted deposits and Mississippi Valley-type (MVT) deposits. Major zinc-producing countries include China, Australia, and Peru.
  7. Lead (Pb): Lead is a versatile metal used in batteries, bullets, and other applications. Lead deposits are typically associated with zinc deposits and can be found in sedimentary-hosted deposits, such as MVT deposits and sedimentary exhalative (SEDEX) deposits. Major lead-producing countries include China, Australia, and the United States.
  8. Tin (Sn): Tin is used in various applications, including electronics, packaging, and soldering. Tin deposits can occur in a variety of forms, including placer deposits, cassiterite-rich veins, and greisen deposits. Major tin-producing countries include China, Indonesia, and Myanmar.

These are just some examples of economically important metal concentrations in the Earth’s crust. There are many other metals and minerals that are economically valuable and used in a wide range of applications, depending on their availability, concentration, and demand in the global market. The extraction and utilization of these metal resources require careful consideration of economic, environmental, and social factors to ensure sustainable resource management.

  1. Aluminum (8.13%)
  2. Iron (5.00%)
  3. Calcium (3.63%)
  4. Sodium (2.83%)
  5. Potassium (2.59%)
  6. Magnesium (2.09%)
  7. Titanium (0.57%)
  8. Hydrogen (0.14%)
  9. Manganese (0.10%)
  10. Phosphorus (0.10%)

Other metals that are economically important include copper, gold, silver, lead, zinc, nickel, and platinum, among others. The concentration of these metals in the Earth’s crust is much lower than the most common metals, with copper being the most abundant at 0.0068%, followed by lead at 0.0013%, zinc at 0.0075%, and nickel at 0.0081%.

Here are some typical background and ore levels of several important metals:

  1. Copper:
  • Background levels: 10-50 ppm
  • Ore levels: 0.5-5% Cu
  1. Gold:
  • Background levels: 0.0005-0.5 ppm
  • Ore levels: 1-20 g/t Au
  1. Silver:
  • Background levels: 0.01-1 ppm
  • Ore levels: 50-800 g/t Ag
  1. Lead:
  • Background levels: 10-50 ppm
  • Ore levels: 3-10% Pb
  1. Zinc:
  • Background levels: 10-150 ppm
  • Ore levels: 3-15% Zn
  1. Nickel:
  • Background levels: 50-200 ppm
  • Ore levels: 0.5-3% Ni

It’s important to note that these levels can vary widely depending on the deposit and location.

Most valuable metal in Earth Crust

The most valuable metal in the Earth’s crust can vary depending on a number of factors such as current market demand, availability, and the cost of extraction. Precious metals, such as gold, platinum, and silver, have historically been highly valued due to their scarcity and unique properties, and are often associated with luxury items and financial instruments. Other metals, such as copper, nickel, and iron, are highly valued for their usefulness in industry and infrastructure, and are considered to be more economically important. However, it’s worth noting that the value of a metal depends not only on its physical properties, but also on the societal, cultural, and economic factors that influence its perceived value.

In terms of the most valuable metal by market price, the answer can vary over time depending on a number of factors, such as supply and demand, geopolitical events, and technological advances. However, historically, some of the most valuable metals in the Earth’s crust have included precious metals like gold, silver, and platinum, as well as rare earth metals like neodymium, yttrium, and cerium. These metals are used in a wide range of applications, including electronics, jewelry, and industrial processes, among others.

It’s worth noting that the value of a metal depends not only on its price but also on its availability, which is influenced by a number of geological, economic, and political factors. For example, a metal may have a high market price, but if it is only found in small quantities or in hard-to-reach locations, its actual value may be limited. Additionally, factors such as production costs, energy requirements, and environmental impact can all affect the overall economic viability of extracting and using a particular metal.

The percentage of valuable metals in the Earth’s crust varies widely, depending on the metal in question. Here are a few examples of the abundance of some valuable metals in the Earth’s crust:

  • Aluminum: 8.1%
  • Copper: 0.0068%
  • Gold: 0.000004 ppm (parts per million)
  • Iron: 5.6%
  • Lead: 0.0013%
  • Platinum: 0.000005 ppm
  • Silver: 0.000075%
  • Uranium: 0.00015%
  • Zinc: 0.0075%

It’s important to note that these figures represent the average abundance of these metals across the entire Earth’s crust, and the actual concentrations can vary widely in different regions and deposits.

Consider Canada, one of the world’s largest manufacturers. Canada has the largest mining regions in the world and has been one of the biggest suppliers for the last 150 years.
Canada earns a lot of income in Canada’s mining industry. Most of these are significant amounts of gold, iron, copper and potash, which are less important than nickel and diamond, but with less amounts. Revenues from the oil sector are higher than $ 100 billion annually.

The value of various Canadian mining sectors in 2013 [SE from data at http://www.nrcan.gc.ca/mining-materials/publications/8772]

A metal deposition is a rock mass in which one or more metals are concentrated to the point where it is economically suitable for recovery. Some background levels of important metals in average rocks are shown in the Table with typical grades required to form a suitable residue and their corresponding concentration factors. For example, when we look at the copper, we see that although the average rock is about 40 ppm (parts per million) of copper, about 10,000 ppm or 1% is required to obtain a suitable copper residue. In other words, copper ore contains 250 times as much copper as the typical rocks. The concentration factors for other elements in the list are much higher. 2,000 for gold and 10,000 for silver.

Typical background and ore levels of some important metals

MetalTypical Background LevelTypical Economic Grade*Concentration Factor
Copper40 ppm10,000 ppm (1%)250 times
Gold0.003 ppm6 ppm (0.006%)2,000 times
Lead10 ppm50,000 ppm (5%5,000 times
Molybdenum1 ppm1,000 ppm (0.1%)1,000 times
Nickel25 ppm20,000 ppm (2%)800 times
Silver0.1 ppm1,000 ppm (0.1%)10,000 times
Uranium2 ppm10,000 ppm (1%)5,000 times
Zinc50 ppm50,000 ppm (5%)1,000 times

It is clear that some very important concentrations need to occur in order to create a precious residue. This concentration may occur during the formation of the host rock or after rock formation by several different types of processes. There are a wide variety of ore forming processes and hundreds of mineral deposits

Magmatic deposits

By
Mahmut MAT
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Magmatic deposits are mineral deposits that are associated with igneous rocks, such as granite, gabbro, and basalt. They are formed by the cooling and crystallization of magma or lava, which can result in the concentration of various minerals within the solidified rock. Magmatic deposits can be further subdivided into two main types: intrusive and extrusive.

Magmatic deposits

Intrusive magmatic deposits, also known as plutonic deposits, are formed when magma solidifies within the Earth’s crust. As the magma cools, minerals begin to crystallize out of the melt and become concentrated in certain parts of the rock. The resulting deposits can be massive in size and can contain high concentrations of valuable minerals, such as copper, nickel, platinum, and gold.

Extrusive magmatic deposits, also known as volcanic deposits, are formed when magma or lava erupts onto the Earth’s surface and solidifies. These deposits can be found in the form of lava flows, volcanic ash, and other volcanic rocks. Some examples of extrusive magmatic deposits include massive sulfide deposits, which are rich in copper, zinc, and lead, and platinum-group element deposits, which are rich in platinum, palladium, and rhodium.

Magmatic deposits can be economically important sources of various metals and minerals, and they are often the targets of mining and exploration activities.

Types of magmatic deposits

Magmatic deposits are formed from magma, which is molten rock that originates from the Earth’s mantle or lower crust. As the magma cools and solidifies, it can concentrate certain elements, which can form deposits of valuable minerals.

There are several types of magmatic deposits, including:

  1. Porphyry Deposits: These are the most common type of magmatic deposit and are typically found in copper and gold mining operations. Porphyry deposits form when magma intrudes into the earth’s crust, and minerals are deposited as the magma cools and solidifies. Porphyry deposits are generally low-grade but large-tonnage operations that require significant amounts of processing.
  2. Skarn Deposits: Skarn deposits are formed by the interaction of magma with carbonate rocks. The heat and fluids from the magma alter the carbonate rocks, creating a zone of mineralization called a skarn. Skarn deposits are known for their high-grade deposits of copper, gold, silver, and tungsten.
  3. Pegmatite Deposits: These deposits are known for their coarse-grained nature, which makes them easier to mine. Pegmatites are formed from the late-stage cooling of magma and contain a variety of minerals, including rare earth elements, lithium, and tantalum. Pegmatite deposits are usually small, but the high concentration of valuable minerals can make them economically viable.
  4. Kimberlite Deposits: Kimberlite deposits are formed from the eruption of deep-source magma and are known for their diamond-bearing nature. The volcanic eruptions bring the diamonds to the surface, where they can be mined. However, the diamond deposits within kimberlite are generally small and sporadic, making mining operations difficult and costly.
  5. Carbonatite Deposits: These deposits are formed by the cooling and solidification of carbonatite magma. Carbonatite deposits are known for their rare earth element deposits and are typically mined for these elements, which are used in high-tech applications.

Each of these magmatic deposits has its own unique characteristics, and their economic viability depends on a variety of factors, including the grade and tonnage of the deposit, the accessibility of the deposit, and the market demand for the minerals contained within the deposit.

Porphyry Deposits

Porphyry Deposits Model

Porphyry deposits are a type of magmatic deposit that are economically important sources of copper, molybdenum, and gold, as well as other metals. They are named after the texture of the rocks that host the mineralization, which consists of large crystals, or phenocrysts, embedded in a finer-grained matrix, or groundmass.

Porphyry deposits are formed by the intrusion of magmas into the Earth’s crust, which can create large, deep-seated magma chambers. As these chambers cool and solidify, hydrothermal fluids are released, which can carry metals and other elements. These fluids migrate through fractures and other permeable structures in the surrounding rock, and can precipitate mineralization as they cool and interact with the host rocks.

Porphyry deposits are typically large and low-grade, with mineralization occurring over broad areas. They can also be polymetallic, meaning that they contain multiple metals of economic interest. Some of the world’s largest copper and gold mines are porphyry deposits, including the Bingham Canyon mine in Utah, USA, and the Grasberg mine in Indonesia.

Skarn Deposits

Skarn Deposits

Skarn deposits are formed when hydrothermal fluids interact with carbonate-rich rocks, such as limestone or marble, resulting in the replacement of the original minerals by a variety of minerals, including those of economic interest. Skarns can host a wide range of metallic minerals, including copper, gold, silver, lead, zinc, tungsten, and molybdenum.

The formation of skarn deposits typically involves the following process:

  1. Intrusion of igneous rocks, which provide a heat and fluid source.
  2. Interaction of the igneous rocks with carbonate-rich sedimentary rocks, leading to the replacement of the carbonate minerals with new minerals.
  3. Deposition of economic minerals within the skarn.

Skarn deposits are often associated with porphyry deposits, as both are typically formed by the same hydrothermal system. Examples of skarn deposits include the Antamina deposit in Peru and the Mt. Skukum deposit in Canada.

Pegmatite Deposits

Pegmatite Deposits

Pegmatite deposits are a type of magmatic deposit that are composed of unusually large crystals or masses of minerals that are commonly formed in the final stages of the crystallization of a magma. Pegmatites are generally coarse-grained and often contain rare or unusual minerals, making them of interest to mineral collectors and occasionally of economic interest. Some of the minerals commonly found in pegmatites include feldspar, mica, quartz, tourmaline, topaz, and beryl.

Pegmatites are typically found in association with granite, and they are commonly emplaced along the margins of granite plutons or within the plutons themselves. They can also occur as dikes or veins that cut across other rocks. The formation of pegmatites is thought to be related to the slow cooling of the magma and the consequent growth of large crystals, as well as to the presence of water and other volatile elements in the magma. Because of their unusual mineralogy and large crystal size, pegmatites can sometimes be important sources of industrial minerals, gemstones, and rare metals.

Kimberlite Deposits

Kimberlite Deposits

Kimberlite is a type of rock that is known for containing diamonds. Kimberlite is named after the town of Kimberley in South Africa, where the first diamonds found in kimberlite were discovered. Kimberlite is a type of volcanic rock that is formed from magma that rises from the Earth’s mantle and cools relatively quickly, preserving many of the mantle’s characteristics. Kimberlite pipes are the most important source of diamonds in the world. The diamonds in kimberlite pipes are thought to have originated deep in the Earth’s mantle and were brought to the surface by volcanic activity. Other minerals found in kimberlite include olivine, pyroxene, and garnet.

Carbonatite Deposits

Carbonatite Deposits

arbonatite deposits are another type of magmatic deposit that are relatively rare but can be economically important. These deposits are characterized by their high concentrations of rare earth elements (REE), which are used in a variety of high-tech applications, such as electronics, magnets, and batteries.

Carbonatites are igneous rocks that are composed primarily of carbonate minerals, such as calcite and dolomite, as well as other minerals, such as apatite, magnetite, and phlogopite. They are believed to form from carbonatitic magma that originates deep within the mantle and rises to the surface, either directly or through the process of assimilation, where it cools and solidifies.

The Bayan Obo deposit in China is one of the largest carbonatite deposits in the world and is a major source of REEs. Other notable carbonatite deposits include the Palabora complex in South Africa, the Mount Weld deposit in Australia, and the Mountain Pass deposit in the United States.

Formation processes and mineralogy

Magmatic deposits form from the cooling and crystallization of magma, which can lead to the concentration of certain minerals into economic deposits. The mineralogy of magmatic deposits depends on the composition of the original magma and the conditions under which it cooled and crystallized.

The minerals commonly associated with magmatic deposits include sulfides, oxides, and silicates of metals such as copper, nickel, platinum, palladium, gold, and silver. These metals tend to be more concentrated in the denser and heavier minerals, which sink to the bottom of the magma chamber during the cooling and solidification process.

The mineralogy of magmatic deposits can also be influenced by the presence of volatile elements such as sulfur, chlorine, and fluorine, which can cause the formation of minerals such as apatite, magnetite, and fluorite. In addition, the cooling and solidification of magma can lead to the formation of minerals such as feldspar, mica, and quartz, which can sometimes be economically valuable.

Examples of notable magmatic deposits

There are many notable magmatic deposits around the world. Here are a few examples:

  1. Norilsk-Talnakh, Russia: This deposit is one of the largest sources of nickel and palladium in the world. It is located in the Siberian Traps, which are part of a large igneous province that was formed during the Permian-Triassic extinction event.
  2. Bushveld Complex, South Africa: This layered mafic intrusion is one of the world’s largest sources of platinum and chromium. The deposit is about 2 billion years old and covers an area of about 66,000 square kilometers.
  3. Sudbury Basin, Canada: This basin is one of the largest impact structures on Earth and contains a massive magmatic deposit that is rich in nickel, copper, and platinum group metals. The deposit was formed by a meteorite impact about 1.8 billion years ago.
  4. Palabora, South Africa: This deposit is one of the world’s largest sources of copper and contains significant amounts of gold and silver. It is located in a large carbonatite complex that was formed about 2 billion years ago.
  5. Stillwater Complex, USA: This layered mafic intrusion in Montana is a major source of platinum group metals and contains significant amounts of chromium and copper. The deposit is about 2.7 billion years old and covers an area of about 2,600 square kilometers.

These deposits are just a few examples of the many magmatic deposits that have been discovered around the world.

Manganite

By
Mahmut MAT
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Manganite, Northern Cape Province, South Africa
Manganite, Thuringia, Germany
Manganite, Northern Cape Province, South Africa

Manganite is a member of oxide minerals with composed of manganese oxide-hydroxide of formula: MnO(OH).A widespread and important ore of manganese. The mineral had been described by a number of different names since 1772, but was finally given its current name, which it owes to its manganese component, in 1827. Opaque and metallic dark gray or black, crystals of manganite are mostly pseudoorthorhombic prisms, typically with flat or blunt terminations, and are often grouped in bundles and striated lengthwise. Multiple twinning is common. Manganite can also be massive or granular; it is then hard to distinguish by eye from other manganese oxides, such as pyrolusite. An important ore of manganese, manganite occurs in hydrothermal deposits formed at low temperature (up to 400°F/200°C) with calcite, siderite, and barite, and in replacement deposits with goethite. Manganite also occurs in hot-spring manganese deposits. It alters to pyrolusite and may form by the alteration of other manganese minerals.

The mineral contains 89.7% manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine.

Name: For MANGANese in the composition.

Association: Pyrolusite, braunite, hausmannite, barite, calcite, siderite, goethite.

Polymorphism & Series: Trimorphous with feitknechtite and groutite

Environment: In low temperature hydrothermal replacement deposits, acid-rich bogs, and in manganese-rich hot springs.

Composition: MnO(OH). Mn = 62.4 per cent, 0 = 27.3 percent, H20 = 10.3 percent.

Diagnostic Features: Told chiefly by its black color, prismatic crystals, hardness (4), and brown streak. The last two will serve to distinguish it from pyrolusite.

Crystallography: Orthorhombic; dipyramidal. Crystals usually long prismatic with obtuse terminations, deeply striated vertically. Often twinned. Crystals often grouped in bundles or in radiating masses; also columnar.

Chemical Properties

Chemical Classification Oxide mineral
Formula MnO(OH)
Common Impurities Fe,Ba,Pb,Cu,Al,Ca

Manganite Physical Properties

Crystal habit Slender prismatic crystals, massive to fibrous, pseudo-orthorhombic
Color Gray-black, black
Streak Reddish brown to black
Luster Resinous, Sub-Metallic, Dull
Cleavage Perfect {010} perfect; {110} and {001} good.
Diaphaneity Opaque
Mohs Hardness 4
Crystal System Monoclinic
Tenacity Brittle
Density 4.29 – 4.34 g/cm3 (Measured)    4.38 g/cm3 (Calculated)
Fracture Splintery

Manganite Optical Properties

Type Anisotropic
Anisotropism Weak
Color / Pleochroism Weak
2V: Small
RI values: nα = 2.250(2) nβ = 2.250(2) nγ = 2.530(2)
Twinning Contact and penetration Twins on {011}; lamellar on {100}.
Optic Sign Biaxial (+)
Birefringence 0.028
Relief Very High
Dispersion: r > v extreme

Occurrence

Formed in low-temperature hydrothermal or hot-spring manganese deposits; replacing other manganese minerals in sedimentary deposits; a component in some clay deposits and laterites.

Manganite is found associated with other manganese oxides and has a similar origin. It frequently alters to pyrolusite. Found often in veins associated with the granitic igneous rocks, both filling cavities and as a replacement of the neighboring rocks. Barite and calcitc are frequent associates.

Manganite Uses Area

  • A minor ore of manganese.
  • In mineral prehistoric times, a pigment has been used by humans and as the igniter of Neanderthals. Manganite is believed to be used in prehistoric times to burn wood fire. Manganite reduces the combustion temperature of the wood from 350 degrees Celsius to 250 degrees Celsius. Manganite dust is a common finding in Neanderthal archaeological sites.

Distribution

Many localities, but rarely well-crystallized.

  • Fine crystals from Ilfeld, Harz Mountains, and Ilmenau, Thuringia, Germany.
  • In the Botallack mine, St. Just, Cornwall; from Egremont, Cumbria; and at Upton Pyne, Exeter, Devonshire, England.
  • From Granam, near Towie, Aberdeenshire, Scotland.
  • At Bolet, near Karlsborg, Vastergotland,Sweden.
  • In the USA, good crystals from the Negaunee and Marquette districts, Marquette Co., Michigan; in the Powell’s Fort mine, near Woodstock, Shenandoah Co., Virginia; and at Lake Valley, Sierra Co., New Mexico.
  • From the Caland mine, Atikokan, Ontario, Canada.
  • At Kuruman, Cape Province, South Africa.

Reference

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].

Turquoise

By
Mahmut MAT
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Turquoise-pyrite-quartz
Turquoise, Bishop Mine, River Manganese District, Campbell County, Virginia, USA
Turquoise pebble, made by tumbling the rough rock in a rotating drum with abrasive.

Turquoise is a member of phosphate mineral with chemical the formula CuAl6 (PO4)4(OH) 8·4H2O. Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium. Beads made of turquoise that date back to c.5000 BCE have been recovered in Mesopotamia (present-day Iraq). This mineral usually occurs in massive or microcrystalline forms, as encrustations or nodules, or in veins. Crystals are rare; when found, they occur as short, often transparent prisms. Turquoise varies in color from sky-blue to green, depending on the amount of iron and copper it contains. Turquoise occurs in arid environments as a secondary mineral probably derived from the decomposition of apatite and some copper sulfides. One of the first gemstones to be mined. It is uncommon and precious in the finer grades and has been offered as gemstone and ornamental stones for hundreds of years because of its unique tone. Recently, turquoise, like many other opaque jewels, has been devalued with access into the market of treatments, imitations and synthetics.

Formation

As a secondary mineral, turquoise is formed through the leaching impact of acidic aqueous answers for the duration of the decomposition and oxidation of pre-existing minerals. As an example, copper can also come from number one copper sulphides such as chalcopyrite or from secondary carbonates of malachite or azurite; derived from aluminum feldspar; and phosphorus from apatite. Because turquoise is regularly discovered in arid areas, generally in crammed or volcanic rocks, often in turquoise regions that fill or absorb cavities and cracks filled with related limonite and different iron oxides, weather factors play an critical role. Inside the southwestern u.s.a., turquoise is sort of continually unchanged with the decomposition merchandise of copper sulphide deposits in or round potassium-feldspar-containing porphyritic interventions. In some formations, alunite, potassium aluminum sulfate, is a distinguished secondary mineral. Typically turquoise mineralization is constrained to a shallow intensity of much less than 20 meters (66 ft), but happens at deeper fracture zones wherein the secondary solutions have greater penetration or the intensity of the water desk is greater.

Chemical Properties

Chemical Classification Phosphate minerals
Formula CuAl6(PO4)4(OH)8·4H2O
Common Impurities Fe,Ca

Name: Turquois is French and means Turkish, the original stones having come into Europe from the Iranian locality through Turkey.

Association: Kaolinite, montmorillonite, allophane, wavellite, pyrite.

Polymorphism & Series: Forms two series, with chalcosiderite, and with planerite.

Mineral Group: Turquoise group

Crystallography: Triclinic; pinacoidal. Rarely in minute crystals, usually cryptocrystalline. Massive compact, reniform,- stalactitic. In thin seams, incrustations and disseminated grains.

Turquoise Composition: A basic hydrous phosphate of aluminum, Al2 (0H)3P04- H20. Excluding CuO reported in chemical analyses of turquois, the percentages of the oxides are: A120 3 = 46.8, P2Or, = 32.6, H20 = 20.6. The mineral is colored by small amounts of copper whose role in the composition is not well understood.

Diagnostic Features: Turquois can be easily recognized by its color. It is harder than ehrysocolla, the only common mineral which it resembles.

Turquoise Uses: As a gem stone. It is always cut in round or oval forms. Much turquois is cut which is veined with the various gangue materials, and such stones are sold under the name of turquois matrix.

Turquoise Physical Properties

Crystal habit Massive, nodular
Color Bright blue, sky-blue, pale green, blue-green, turquoise-blue, apple-green, green-gray
Streak Pale greenish blue to white
Luster Sub-Vitreous, Resinous, Waxy, Dull, Earthy
Cleavage Perfect on {001}, good on {010}
Diaphaneity Transparent, Translucent, Opaque
Mohs Hardness 5 – 6
Crystal System Triclinic
Tenacity Brittle
Density 2.6 – 2.8 g/cm3 (Measured)    2.91 g/cm3 (Calculated) (Mindat.com)
Fracture Irregular/Uneven, Sub-Conchoidal
Fusibility Fusible in heated
Solubility Soluble in HCl

Occurrence of Turquoise

Turquoise become most of the first mined stones, and even though a number of them are still studied today, many historical web sites are extinct. Those are all small-scale operations; because of the limited scope and distance of deposits, they’re generally seasonal. Most manually perform with very little mechanization. However, turquoise is often recycled as a of massive-scale copper mining operations, particularly within the United States of America.

Iran: Iran has been vital turquoise source for at least 2,000 years. It was to begin with called “pērōzah” by the Iranians, meaning “victory”, after which the Arabs were known as “fayrūzah”, which changed into mentioned “fīrūzeh” in contemporary Persian. In Iranian structure, blue turned into used to cover the domes of turquoise palaces, due to the fact the intense blue colour changed into additionally a symbol of heaven on earth.

Sinai: as a minimum the primary Dynasty (BCE 3000) in historical Egypt, and probably earlier than it, turned into utilized by the turquoise Egyptians and became extracted by means of them in the Sinai Peninsula. This vicinity turned into regarded by the local Monitu as the Turquoise use. There are six mines at the southwest coast of the peninsula, overlaying an area of ​​approximately 650 rectangular kilometers (250 square meters). The maximum vital of these mines are Serabit al-Khadim and Wadi Maghareh, traditionally believed to be one of the oldest known mines. The historic mine is ready four kilometers from an historical temple devoted to the gods Hathor.

USA: The Southwest United States is a crucial turquoise supply; Arizona, California (San Bernardino, Imperial, Inyo counties), Colorado (Conejos, El Paso, Lake, Saguache counties), New Mexico (Eddy, grant, Otero, Santa Fe counties) and Nevada (Clark, Elko, Esmeralda County, Eureka) Lander, Mineral County and Nye counties). California and New Mexico’s deposits had been extracted by way of native individuals, pre-Columbian, using stone equipment, a few nearby and a few as far flung as valuable Mexico. Cerrillos is notion to be the website of the oldest mines in New Mexico; before the Nineteen Twenties the country was the USA’s largest producer; extra or much less exhausted today. A mine positioned within the Apache Canyon in California is currently in industrial ability.

Different Sources: Turquoise prehistoric artifacts (beads) had been regarded from BCE’s regions inside the Japanese Rhodopes in Bulgaria for the fifth millennium – the supply of uncooked materials is probably associated with the close by Spahievo lead-zinc ore field.

China has been a small turquoise supply for extra than 3000 years. The jewel-great fabric inside the shape of compact nodules is observed inside the damaged, silicified limestones of Yunxian and Zhushan in Hubei province. Further, Marco Polo pronounced the presence of turquoise in contemporary Sichuan. Maximum Chinese materials are exported, but there are numerous carvings carved like jade. In Tibet, the Derge and Nagari-Khorsum mountains in the east and west of the place are claimed to have jewel-first-rate deposits.

Different noteworthy places are: Afghanistan; Australia (Victoria and Queensland); North India; Northern Chile (Chuquicamata); Cornwall; Saxony; Silesia; and Turkestan.

Turquoise Optical Properties

Color / Pleochroism Weak X= colorless Z= pale blue or pale green
2V: Measured: 40° , Calculated: 44°
RI values: nα = 1.610 nβ = 1.615 nγ = 1.650
Optic Sign Biaxial (+)
Birefringence 0.040
Relief Moderate
Dispersion: r < v strong

Distribution

Dozens of localities, of which only a few can be mentioned, for commercial amounts or good crystals.

  • In Iran, at Madan, 45 km northwest of Neyshabur (Nishapur).
  • From Ottre, near Vielsalm, Belgium.
  • At the Bunny mine, St. Austell, and elsewhere in Cornwall, England.
  • From Katonto, north of Kolwezi, Katanga Province, Congo (Shaba Province, Zaire), good crystals.
  • In the USA, crystallized from the Bishop mine, Lynch Station, Campbell Co., Virginia; in the Cerrillos district, Santa Fe Co., and the Burro Mountains district, Grant Co., New Mexico; in Arizona, commercial production from Mineral Park, Mohave Co., Morenci, Greenlee Co., the Globe-Miami district, Gila Co., and others; numerous small deposits in Lander Co. and elsewhere in Nevada.
  • In the Itatiaiucu iron mine, southwest of Belo Horizonte, Minas Gerais, Brazil, large crystals.
  • At Chuquicamata, Antofagasta, Chile.
  • In Australia, at Narooma, New South Wales, as crystals; in the Iron Monarch quarry, Iron Knob, South Australia.
  • In China, from Yunxian and Zhushan, Wudang Mountains, Hubei Province, and near Shanyang, Shaanxi Province.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
  • Wikipedia contributors. (2019, June 25). Turquoise. In Wikipedia, The Free Encyclopedia. Retrieved 02:25, July 9, 2019, from https://en.wikipedia.org/w/index.php?title=Turquoise&oldid=903470553

Chrysoberyl

By
Mahmut MAT
-

Chrysoberyl is a mineral and gemstone that belongs to the beryl family. It is known for its unique optical properties, durability, and various color varieties. The name “chrysoberyl” is derived from the Greek words “chrysos” meaning gold and “beryllos” meaning beryl, which reflects the golden to greenish hues that are commonly associated with this mineral.

Chrysoberyl
chrysoberyl var. alexandrite
chrysoberyl var. alexandrite under UV light long waves

Chrysoberyl is a beryllium aluminum oxide mineral with the chemical formula BeAl2O4. It forms in the orthorhombic crystal system and is typically found as prismatic crystals. Chrysoberyl is most renowned for its exceptional hardness (8.5 on the Mohs scale) and its pleochroism, which is the ability to display different colors when viewed from different angles.

Chemical Composition and Crystal Structure:

The chemical composition of chrysoberyl consists of beryllium, aluminum, and oxygen. It is composed of a three-dimensional framework of aluminum and beryllium ions bonded to oxygen atoms. The specific arrangement of these atoms gives rise to the crystal structure of chrysoberyl.

Chrysoberyl crystals are usually elongated and can be found in various colors, including yellow, green, brown, and even colorless. The greenish-yellow to yellowish-green variety is the most well-known and is often referred to simply as “chrysoberyl.” Another notable variety is “alexandrite,” which exhibits a unique color-changing property, appearing green in daylight and red under incandescent light.

Historical Significance and Uses:

Chrysoberyl has a long history of use as a gemstone and has been valued for centuries. The most famous variety, alexandrite, was first discovered in the Ural Mountains of Russia in the 1830s and was named after the Russian tsar, Alexander II. Alexandrite’s remarkable color-changing ability made it particularly cherished among collectors and jewelry enthusiasts.

Chrysoberyl’s hardness and durability make it suitable for various jewelry applications, especially for items like rings and earrings that are exposed to daily wear. While alexandrite is a rare and sought-after collector’s gem, other chrysoberyl varieties, such as the cat’s-eye chrysoberyl, are also popular due to their unique optical phenomena.

In addition to its use in jewelry, chrysoberyl has been used in some scientific and industrial applications due to its resistance to heat, chemicals, and abrasion. However, its primary appeal lies in its use as a gemstone prized for its beauty, durability, and exceptional optical properties.

Types and Varieties of Chrysoberyl

Chrysoberyl is a mineral that comes in various types and varieties, each with its own unique characteristics and colors. Here are some of the most notable types and varieties of chrysoberyl:

  1. Chrysoberyl: This is the general term used to refer to the yellow, yellow-green, or greenish-yellow variety of the mineral. It is often valued for its brilliance and durability, making it a popular choice for gemstone jewelry. While it lacks the color-changing property of alexandrite, it still possesses the pleochroic effect that can give it different colors when viewed from different angles.
  2. Alexandrite: Alexandrite is one of the most famous and valuable varieties of chrysoberyl due to its unique color-changing property. It appears green in natural daylight and shifts to a reddish or purplish hue under incandescent light. This dramatic color change is a result of the presence of chromium in its crystal structure. Alexandrite is highly sought after by collectors and gem enthusiasts for its rarity and mesmerizing optical characteristics.
  3. Cat’s-Eye Chrysoberyl: This variety of chrysoberyl exhibits a captivating phenomenon known as chatoyancy or the “cat’s-eye effect.” When cut as a cabochon, it displays a bright, narrow band of light that appears to glide across the surface of the gemstone when it’s moved. This effect is caused by needle-like inclusions of fibers or tubes within the crystal structure that reflect light in a concentrated line. The cat’s-eye effect can be seen in various colors of chrysoberyl, including yellow, green, and brown.
  4. Cymophane: Cymophane is another name for cat’s-eye chrysoberyl due to its distinctive chatoyant effect. The term “cymophane” comes from the Greek words “kyma,” meaning wave, and “phanos,” meaning appearance, referring to the wavy appearance of the cat’s-eye effect.
  5. Yellow Chrysoberyl: This variety of chrysoberyl is valued for its pure yellow color. It lacks the strong green hues found in some other varieties and is often cut into faceted gemstones for use in jewelry.
  6. Green Chrysoberyl: This variety leans more toward green hues than the yellow varieties. It can vary in shades from pale green to a more intense, vibrant green. Green chrysoberyl is often used in jewelry as well, and its durability makes it suitable for various types of jewelry settings.
  7. Brown Chrysoberyl: Brown chrysoberyl is less common and tends to be less valued for gemstone use compared to other color varieties. It can still display the pleochroic effect but is less popular due to its less attractive color.
  8. Colorless Chrysoberyl: While colorless chrysoberyl lacks the vibrant hues of other varieties, its brilliance and hardness still make it a valuable gemstone for certain jewelry designs. It is relatively rare and can be used as an alternative to diamond in some instances.

These are some of the main types and varieties of chrysoberyl, each with its own distinctive features and appeal. Whether valued for their color-changing properties, chatoyancy, or vivid colors, chrysoberyl gemstones have captured the fascination of gem enthusiasts and collectors around the world.

Physical Properties of Chrysoberyl

Chrysoberyl is a mineral with several distinctive physical properties:

  • Color: Chrysoberyl occurs in a range of colors, including yellow, green, brown, and colorless. The most well-known color variety is the yellow to greenish-yellow, often referred to as simply “chrysoberyl.” The color can vary based on trace elements present in the crystal structure.
  • Crystal Structure: Chrysoberyl crystallizes in the orthorhombic crystal system. It typically forms prismatic crystals that can be elongated. The crystal structure is what gives rise to its unique optical properties.
  • Hardness: Chrysoberyl is one of the hardest gemstones, with a hardness of 8.5 on the Mohs scale. This makes it highly resistant to scratching and abrasion, making it suitable for everyday jewelry wear.
  • Cleavage: Chrysoberyl has poor to indistinct cleavage, meaning it doesn’t break along well-defined planes like some other minerals. Instead, it tends to fracture conchoidally, producing smooth, curved surfaces when broken.
  • Specific Gravity: The specific gravity of chrysoberyl typically ranges from 3.5 to 3.8, indicating its relatively high density.

Color Variations and Phenomena:

Chrysoberyl exhibits various color variations and optical phenomena that contribute to its allure:

  • Color Change: The most famous color-changing variety of chrysoberyl is alexandrite. This gemstone displays a remarkable color change from green or bluish-green in daylight to purplish-red or reddish-purple under incandescent light. This phenomenon is caused by the presence of chromium and its interaction with light.
  • Pleochroism: Chrysoberyl is pleochroic, which means it can display different colors when viewed from different angles. This is particularly noticeable in the green to yellow varieties, where the gem may appear green when viewed from one angle and yellow from another.

Hardness and Durability:

Chrysoberyl’s exceptional hardness and durability make it highly resistant to wear and damage:

  • Hardness: With a hardness of 8.5 on the Mohs scale, chrysoberyl is surpassed in hardness only by a few gemstones like diamond, corundum (sapphire and ruby), and moissanite. Its hardness ensures that it can withstand daily wear without easily acquiring scratches.
  • Durability: Chrysoberyl’s hardness also contributes to its overall durability. It is resistant to scratching, chipping, and abrasion, making it suitable for a wide range of jewelry applications.

Optical Characteristics and Luster:

Chrysoberyl’s optical properties enhance its visual appeal and contribute to its desirability:

  • Luster: Chrysoberyl has a vitreous to adamantine luster, giving it a bright and reflective appearance when well-polished.
  • Chatoyancy (Cat’s-Eye Effect): In cat’s-eye chrysoberyl, a phenomenon known as chatoyancy occurs. When cut as a cabochon, a distinct band of light, resembling a cat’s-eye, appears to glide across the surface of the gemstone when it’s moved. This effect is caused by the presence of fibrous or tubular inclusions that reflect light in a concentrated line.
  • Color Saturation: The color saturation of chrysoberyl can vary, affecting its visual impact. Intensely colored varieties, such as the vibrant green or golden-yellow ones, are particularly prized.

In summary, chrysoberyl’s physical properties, including its color variations, unique optical phenomena, exceptional hardness, and luster, contribute to its appeal as a valued and versatile gemstone for jewelry and collectors alike.

Geological Occurrence

Chrysoberyl (beryllium aluminium oxide) from the Ural Mountains in the Perm province of Russia. Cotton Collection, Keele.

Chrysoberyl is primarily formed in pegmatite veins, which are coarse-grained igneous rocks found in various geological settings. It often occurs in association with other minerals and gemstones, such as beryl (including emerald and aquamarine), mica, feldspar, and quartz. Chrysoberyl can also be found in metamorphic rocks, particularly those that have undergone high-pressure and high-temperature conditions.

Formation Processes:

The formation of chrysoberyl involves geological processes that occur deep within the Earth’s crust:

  1. Pegmatite Formation: Chrysoberyl commonly forms in pegmatite veins, which are formed during the late stages of crystallization of molten rock (magma). Pegmatites are known for producing larger crystals due to their slow cooling and the availability of various elements during the crystallization process.
  2. Metamorphism: Chrysoberyl can also form through metamorphic processes. When pre-existing minerals are subjected to high pressure and temperature conditions within the Earth’s crust, they can transform into new minerals. Chrysoberyl may form as a result of such transformations under specific metamorphic conditions.

Geological Locations and Deposits:

Chrysoberyl can be found in various locations around the world. Some notable deposits include:

  1. Brazil: Brazil is one of the most significant sources of chrysoberyl. It produces both the yellow and green varieties, including cat’s-eye chrysoberyl. Minas Gerais, a Brazilian state, is particularly famous for producing high-quality chrysoberyl.
  2. Sri Lanka: Sri Lanka is known for its production of chrysoberyl, including cat’s-eye chrysoberyl. The gemstone deposits in Sri Lanka have been known for centuries and have contributed to the global supply of chrysoberyl.
  3. Russia: Russia, specifically the Ural Mountains, is historically significant for the discovery of alexandrite in the early 19th century. Alexandrite’s unique color-changing property has made it highly sought after among collectors.
  4. Madagascar: Madagascar is another source of chrysoberyl, including both cat’s-eye and non-cat’s-eye varieties. The island nation has produced a range of chrysoberyl colors, adding to the gemstone’s global availability.
  5. India: Chrysoberyl can also be found in various regions of India. While not as well-known as some other sources, India has contributed to the overall supply of chrysoberyl.
  6. Other Locations: Chrysoberyl can also be found in smaller quantities in other countries, including Myanmar (Burma), Zimbabwe, Tanzania, and the United States.

It’s important to note that the quality and quantity of chrysoberyl deposits can vary from location to location. Additionally, the specific color varieties and optical phenomena found in chrysoberyl can make certain deposits more valuable or sought after by collectors and gem enthusiasts.

Alexandrite: The Color-Changing Gem

Alexandrite is a remarkable and highly prized variety of chrysoberyl due to its exceptional color-changing property. This unique gemstone is known for its ability to exhibit different colors under varying lighting conditions, making it a true marvel of the mineral world.

Color-Changing Phenomenon:

The most distinctive feature of alexandrite is its ability to change color depending on the light source. This phenomenon, known as the “alexandrite effect,” is a result of the gem’s interaction with different wavelengths of light. Alexandrite appears green in daylight or natural light and shifts to a reddish or purplish hue under incandescent or artificial light.

This color change is a result of the presence of trace amounts of chromium in the crystal structure of alexandrite. Chromium absorbs certain wavelengths of light and emits others, causing the gemstone to display different colors depending on the light source’s composition. The precise combination of chromium content, the crystal lattice, and the lighting conditions contribute to the gem’s unique dual-color appearance.

chrysoberyl var. alexandrite under UV light long waves

Discovery and Naming:

Alexandrite was first discovered in the Ural Mountains of Russia in the early 1830s. It was named after Alexander II, the future Russian tsar, to honor his coming of age. The green and red colors of alexandrite also happened to be the primary colors of the Russian imperial army. This naming was a fitting tribute to the young heir to the throne.

Desirable Color Combinations:

The most valued alexandrite specimens exhibit the most dramatic and pronounced color change—changing from a vibrant green or bluish-green in daylight to a vivid red or purplish-red under incandescent light. The more distinct the contrast between the colors and the more intense the hues, the more valuable the alexandrite is considered.

Rarity and Collectibility:

Alexandrite is incredibly rare, and high-quality specimens are among the most valuable gemstones in the world. Factors contributing to its rarity include the specific conditions required for the presence of chromium, the necessary geological processes, and the unique optical properties that make true alexandrite so uncommon.

Due to its scarcity and mesmerizing color-changing ability, alexandrite has captured the attention of gem collectors, jewelry enthusiasts, and connoisseurs for centuries. The gemstone’s scarcity, combined with its captivating optical properties, has led to its status as one of the most sought-after and treasured gems in the world.

In summary, alexandrite stands out as a stunning example of nature’s artistry, showcasing the fascinating color-changing phenomenon caused by the presence of chromium. Its rarity, captivating appearance, and historical significance make it a prized gemstone that continues to captivate those who have the opportunity to admire its remarkable colors.

Cat’s Eye Chrysoberyl: The Phenomenal Gem

Cat’s Eye Chrysoberyl is a captivating and highly sought-after variety of chrysoberyl known for its mesmerizing optical phenomenon called chatoyancy, which creates the appearance of a distinct band of light resembling a cat’s eye moving across the surface of the gemstone. This unique effect makes Cat’s Eye Chrysoberyl a remarkable and cherished gemstone among collectors and jewelry enthusiasts.

Chatoyancy (Cat’s-Eye Effect):

The cat’s-eye effect displayed by Cat’s Eye Chrysoberyl is a result of a specific type of inclusion within the gemstone. Inclusions are minute features trapped within the crystal structure during its formation. In the case of cat’s-eye chrysoberyl, these inclusions are often composed of fine, parallel-oriented fibers or tubes known as “silk.” The inclusions are distributed in such a way that they intersect the surface of the gemstone perpendicular to its length.

When light enters the gemstone and interacts with these fine inclusions, it is reflected along the length of the fibers or tubes. This concentrated reflection creates a luminous band of light that appears as a single bright line across the surface of the gem, reminiscent of the slit-shaped pupil of a cat’s eye. As the gem is moved or rotated, this band of light appears to move as well, creating the illusion of a “cat’s eye” opening and closing.

Formation of Chatoyant Effect:

The chatoyant effect in Cat’s Eye Chrysoberyl is a result of the gem’s growth process. During the gem’s formation within pegmatite veins or metamorphic environments, mineral-rich fluids containing beryllium, aluminum, and other elements slowly crystallize, allowing fine inclusions like silk to become aligned in parallel patterns. These aligned inclusions are what give rise to the unique cat’s-eye effect.

Variety of Colors:

Cat’s Eye Chrysoberyl can exhibit a range of colors, including golden-yellow, green, brown, and gray. The most valued colors are typically the more intense shades of green and golden-yellow. The cat’s-eye effect is especially pronounced in well-cut cabochon gemstones, where the light is concentrated along the length of the silk inclusions.

Value and Rarity:

Cat’s Eye Chrysoberyl is highly valued due to its rarity and the mesmerizing chatoyant effect. The quality of the chatoyancy, the intensity of the color, the sharpness of the cat’s-eye band, and the overall clarity of the gemstone all influence its value. Premium cat’s-eye chrysoberyl gemstones with well-defined, bright, and centered bands of light are considered exceptionally valuable and can command high prices in the market.

Symbolism and Use:

Cat’s Eye Chrysoberyl has been associated with protective and mystical qualities in various cultures. It is believed to bring luck, enhance intuition, and protect its wearer from negative energies. Due to its unique appearance and symbolism, cat’s-eye chrysoberyl is often used in fine jewelry designs, including rings, pendants, and earrings, where its captivating chatoyancy can be prominently displayed and admired.

In conclusion, Cat’s Eye Chrysoberyl’s distinct chatoyant effect, resembling a cat’s eye, sets it apart as a phenomenal gemstone. Its rarity, captivating optical phenomenon, and symbolic significance make it a treasured choice for gem enthusiasts and jewelry aficionados alike.

Gemstone Evaluation and Grading

Gemstone evaluation and grading involve assessing various factors that contribute to a gemstone’s overall quality and value. Different gem types may have specific grading criteria based on their unique characteristics. For chrysoberyl and its varieties like alexandrite and cat’s-eye chrysoberyl, the following factors are considered:

1. Color Grading and Factors:

Color is one of the most important factors in gemstone grading, as it significantly influences a gem’s appearance and value. For chrysoberyl varieties:

  • Hue: The dominant color present in the gem. In chrysoberyl, this can range from yellow and green to brown and colorless.
  • Saturation: The intensity or purity of the color. More saturated colors are generally preferred.
  • Tone: The darkness or lightness of the color. A balanced tone is often more desirable.
  • Color Change (Alexandrite): The degree of color change, the strength of each color, and the contrast between them are crucial factors in evaluating alexandrite.

2. Clarity Assessment:

Clarity refers to the presence of internal characteristics (inclusions) and surface features (blemishes) within the gemstone. Inclusions can vary in size, type, and location. In chrysoberyl and its varieties:

  • Cat’s-Eye Inclusions: For cat’s-eye chrysoberyl, the presence and quality of the silk inclusions that create the chatoyant effect are important. A sharp, centered, and well-defined cat’s-eye band enhances value.
  • Alexandrite Clarity: In alexandrite, clarity is assessed similarly to other gemstones. Gems with fewer and less noticeable inclusions are considered more valuable.

3. Cut and Proportions:

The cut of a gemstone refers to its shape, facet arrangement, and proportions. For chrysoberyl varieties:

  • Cat’s-Eye Cut: In cat’s-eye chrysoberyl, a smooth and symmetrical cabochon cut is preferred to showcase the chatoyant effect. The height and shape of the dome influence the visibility and sharpness of the cat’s-eye.
  • Alexandrite Cut: For alexandrite, a well-executed cut that maximizes color change and brilliance is important. Cutters often aim for a balance between showcasing color change and minimizing color loss.

4. Carat Weight:

Carat weight measures a gemstone’s size, with one carat equaling 200 milligrams. Larger gemstones are generally more valuable, but other factors like color, clarity, and quality of the optical phenomena also play a significant role.

Overall Quality and Value:

Gemstones are evaluated based on how well they combine these factors to create a visually appealing and valuable stone. A well-balanced combination of color, clarity, cut, and carat weight determines a gem’s overall quality and, consequently, its value in the market. Rarity and the presence of unique phenomena like color change and chatoyancy further enhance a gem’s desirability.

Gemstone evaluation is often performed by trained gemologists who use standardized grading systems to provide accurate and consistent assessments of a gemstone’s attributes. These assessments guide pricing, purchasing, and collecting decisions within the gemstone industry.

Chrysoberyl in the Jewelry Industry

Chrysoberyl, with its various color varieties and unique optical phenomena, holds a significant place in the jewelry industry. It is valued not only for its visual appeal but also for its durability and versatility. Here’s how chrysoberyl is used in the jewelry industry:

1. Gemstone Jewelry:

Chrysoberyl is used in a wide range of jewelry pieces, including rings, earrings, necklaces, bracelets, and pendants. Its vibrant colors and eye-catching optical phenomena make it a popular choice for both casual and formal jewelry designs.

  • Alexandrite Rings: Alexandrite, with its color-changing properties, is often featured in engagement and statement rings. The ability to display different colors under various lighting conditions adds an intriguing and dynamic aspect to jewelry pieces.
  • Cat’s-Eye Jewelry: Cat’s Eye Chrysoberyl is typically cut into smooth, rounded cabochons to showcase the cat’s-eye effect. These cabochons are commonly used in rings, pendants, and earrings, allowing the captivating phenomenon to be prominently displayed and admired.

2. Collector’s Items:

High-quality alexandrite and cat’s-eye chrysoberyl gemstones are prized by collectors for their rarity and unique optical phenomena. Collectors often seek stones with well-defined and intense color change or chatoyancy, as these qualities enhance the gem’s value.

3. Custom Jewelry Design:

Chrysoberyl’s range of colors and optical effects provides jewelry designers with opportunities to create custom pieces that highlight the gemstone’s unique qualities. Designers can play with metal choices, settings, and complementary gemstones to enhance the beauty of chrysoberyl.

4. Birthstone and Anniversary Jewelry:

Chrysoberyl’s yellow and green color varieties make it an alternative birthstone for the month of June. It can be used in jewelry pieces to celebrate June birthdays. Additionally, certain anniversaries are associated with chrysoberyl as a symbolic gift choice.

5. Investment Jewelry:

Rare and high-quality chrysoberyl gemstones, especially alexandrite, can appreciate in value over time due to their scarcity. Some individuals choose to invest in such gemstones as a form of alternative investment.

6. Museum and Exhibition Pieces:

Extraordinary chrysoberyl specimens, particularly those with exceptional color-changing or cat’s-eye effects, may find their way into museum collections and exhibitions, showcasing their rarity and aesthetic beauty.

7. Celebrity Endorsement:

When celebrities and public figures wear jewelry featuring unique gemstones like chrysoberyl, it can draw attention to these gemstones and increase their popularity in the fashion and jewelry industries.

In summary, chrysoberyl’s captivating colors, optical phenomena, and durability make it a valuable and sought-after gemstone in the jewelry industry. Its versatility allows it to be used in a variety of jewelry designs, from everyday wear to custom creations, and its rarity adds to its allure for collectors and enthusiasts alike.

Synthetic Chrysoberyl and Imitations

As with many valuable and sought-after gemstones, chrysoberyl has been imitated and synthesized to replicate its appearance. It’s important for consumers, gem enthusiasts, and jewelry professionals to be aware of these synthetics and imitations to ensure they are purchasing genuine and accurately represented gemstones. Here are some common considerations:

1. Synthetic Chrysoberyl:

Synthetic chrysoberyl is created in a laboratory setting using processes that simulate the conditions under which natural chrysoberyl forms. These synthetic stones can closely mimic the appearance of natural chrysoberyl, including color and optical phenomena. Some common methods for creating synthetic chrysoberyl include:

  • Flux Growth: This method involves dissolving chrysoberyl components in a flux and then allowing them to recrystallize under controlled conditions to form synthetic crystals.
  • Hydrothermal Synthesis: Hydrothermal chambers are used to create synthetic chrysoberyl crystals by growing them in a high-pressure, high-temperature environment similar to the conditions in which natural crystals form.

2. Imitations:

Imitations are materials that may look similar to chrysoberyl but are not true chrysoberyl. Some common imitations include:

  • Quartz Cat’s-Eye: Cat’s-eye quartz, which is often gray or brown, can be cut and polished to resemble cat’s-eye chrysoberyl. However, the chatoyant effect in quartz is not as sharp or distinct as in genuine cat’s-eye chrysoberyl.
  • Synthetic Spinel: Certain synthetic spinels may be used to imitate chrysoberyl’s appearance, particularly in its yellow or colorless varieties.

3. Identifying Synthetics and Imitations:

  • Laboratory Reports: Reputable gemological laboratories can provide detailed reports that include information about a gemstone’s origin, treatment, and identity. These reports can help confirm the authenticity of a chrysoberyl.
  • Visual Inspection: Gemologists can use their expertise to visually inspect gemstones for signs of synthetic or imitation materials. For example, some synthetics might exhibit growth features that are not present in natural stones.
  • Equipment: Gemological tools like microscopes, refractometers, and spectrometers can be used to analyze a gemstone’s physical and optical properties, aiding in the identification process.

4. Disclosure:

Ethical and reputable jewelers and sellers should transparently disclose whether a gemstone is natural, synthetic, or an imitation. This information is crucial for consumers to make informed purchasing decisions.

5. Educate Yourself:

If you are considering purchasing a chrysoberyl or any other gemstone, it’s important to educate yourself about the gem’s characteristics, pricing, and common treatments or enhancements. If in doubt, seek the assistance of a qualified gemologist or jeweler to help you evaluate the gemstone’s authenticity.

In summary, while synthetic chrysoberyl and imitations exist, proper education, disclosure, and expert guidance can help ensure that you are acquiring genuine chrysoberyl gemstones with the desired properties and value.

Recap of Key Points

  1. Chrysoberyl Overview:
    • Chrysoberyl is a mineral and gemstone belonging to the beryl family.
    • Its name is derived from the Greek words for “gold” and “beryl,” reflecting its golden to greenish hues.
  2. Types and Varieties:
    • Chrysoberyl comes in various types, including the color-changing alexandrite and the cat’s-eye chrysoberyl with its chatoyant effect.
    • Varieties include yellow, green, brown, colorless, and more.
  3. Physical Properties:
    • Chrysoberyl is known for its hardness (8.5 on the Mohs scale) and durability.
    • It displays pleochroism, showing different colors from different angles.
    • Color change is a unique trait of alexandrite, caused by chromium in its crystal structure.
  4. Geological Occurrence:
    • Chrysoberyl forms in pegmatite veins and metamorphic rocks.
    • Significant sources include Brazil, Sri Lanka, Russia, Madagascar, India, and other locations.
  5. Color Grading and Factors:
    • Color grading involves assessing hue, saturation, and tone.
    • For alexandrite, the color change and contrast are critical.
    • Cat’s-eye chrysoberyl’s chatoyancy is a major factor in evaluation.
  6. Clarity Assessment:
    • Clarity evaluates inclusions and blemishes, which affect transparency.
    • Cat’s-eye chrysoberyl’s silk inclusions create the chatoyant effect.
  7. Cut and Proportions:
    • Cat’s-eye chrysoberyl is often cut into cabochons to display chatoyancy.
    • Alexandrite is cut to optimize color change and brilliance.
  8. Chrysoberyl in Jewelry:
    • Chrysoberyl is used in rings, earrings, necklaces, and more.
    • Alexandrite and cat’s-eye chrysoberyl are popular choices for custom and collector’s jewelry.
  9. Synthetics and Imitations:
    • Synthetic chrysoberyl is created in labs to replicate natural gemstones.
    • Imitations like quartz cat’s-eye and synthetic spinel resemble chrysoberyl’s appearance.
    • Identification involves gemological testing, visual inspection, and reputable sources.
  10. Value and Rarity:
    • High-quality chrysoberyl gemstones, especially alexandrite, can be valuable due to their rarity and unique properties.
    • Proper education and gemological assessments are important for determining value.

Chrysoberyl’s diversity, beauty, and unique optical phenomena have made it a captivating gemstone with historical significance and lasting appeal in the world of jewelry and gem collecting.

Spodumene

By
Mahmut MAT
-
Crystal of bicolor spodumene var. kunzite
Kunzite-Nouristan
Spodumene

Spodumene is a pyroxene member of inosilicate mineral with chemical formula is LiAl(SiO3)2, lithium aluminium. It can also be pink, lilac, or green. Crystals are prismatic, flattened, and typically striated along their length. Gem varieties of the mineral usually exhibit strong pleochroism. Spodumene is an important  ore of lithium. It occurs in lithium-bearing granite pegmatite dykes, often with other lithiumbearing minerals, such as eucryptite and lepidolite. One of the largest single crystals of any mineral ever found was a spodumene specimen from South Dakota, USA, 47 ft (14.3 m) long and 90 tons in weight.

Ordinary low temperature form α-spodumen is found in the monoclinic system, while high-temperature β-spodumen crystallizes in the tetragonal apparatus. Ordinary α-spodumen is converted to β-spodumen at temperatures above 900 ° C. The crystals are generally densely streaked parallel to the main axis. Crystal faces are usually scraped and pitted with triangular markings. (Wiki)

Name: From the Greek for ash-colored, in allusion to its color.

Association: Quartz, albite, petalite, eucryptite, lepidolite, beryl

Mineral Group: Pyroxene group

Chemical Properties

Chemical Classification Inosilicate
Formula LiAl(SiO3)2
Common Impurities Fe,Mn,Mg,Ca,Na,K,H2O

Spodumene Physical Properties

Crystal habit prismatic, generally flattened and elongated, striated parallel to {100}, commonly massive
Color Colourless, yellow, light green, emerald-green, pink to violet, purple, white, gray
Streak White
Luster Vitreous, Dull
Cleavage Perfect
Diaphaneity Transparent, Translucent
Mohs Hardness 6,5 – 7
Crystal System Monoclinic
Tenacity Brittle
Density 3.03–3.23
Fracture Uneven to subconchoidal
Other characteristics Tenebrescence, chatoyancy, kunzite often fluorescent under UV (Wikipedia)
Fusibility         3.5
Solubility         Insoluble

Spodumene Optical Properties

Color / Pleochroism Strong in kunzite: α-purple, γ-colorless; hiddenite: α-green, γ-colorless
2V: Measured: 54° to 69°, Calculated: 88°
RI values: nα = 1.648 – 1.661 nβ = 1.655 – 1.670 nγ = 1.662 – 1.679
Twinning Common on {100}
Optic Sign Biaxial (+)
Birefringence δ = 0.014 – 0.018
Relief Moderate
Dispersion: weak

Occurrence of Spodumene

Spodumen occurs in lithium-rich granite pegmatites, aplites and gneisses. Related minerals are: quartz, albite, petalite, eucryptite, lepidolite and beryl.

The obvious material has been used as a precious stone with its kunzite and hiddenite varieties which have attracted attention with their robust pleochroism for a long time. Resource locations include Afghanistan, Australia, Brazil, Madagascar, Pakistan, Quebec in Canada, and North Carolina, California in the USA.

Uses Area and Economic Importance

Spodumene is an essential supply of lithium to be used in ceramics, cell phones and car batteries, medicine, Pyroceram and as a fluent substance. it’s far extracted from spodumene with the aid of fusing in lithium acid.

World lithium production through spodumen is approximately 80,000 mt per year, mainly from the Greenbushes pegmatite of Western Australia and some Chinese and Chilean sources. The Talison mine at Greenbushes in Western Australia is reported to be the largest and the highest ore level at 2.4% Li2O (2012 figures).

Another important advantage that the spoiler has over the more popular saltwater competitors is the purity of the lithium carbonate it can produce. While all products used by the battery industry are at least 99.5% lithium carbonate, the formation of the remaining 0.5% is important; High amounts of iron, magnesium or other harmful materials make the brine less attractive product.

Gemstone Varieties

Hiddenite: The emerald green spodümen type is colored with chromium like emerald. Not all green spodumens are tinted with chrome, which tends to have a lighter color and is therefore not hidden.

Kunzite: Kunzite is a colorful gemstone that changes from pink to lilac, with a small amount of trace color and various spodumens of manganese colors. Some (not all) used for gemstones are heated to increase the color of kunzite. Also, it is irradiated frequently to improve color.

Triphane: Triphane is a yellow Spodumene variety.

Distribution

  • From Uto, Sodermanland, and in the Varutrask pegmatite, 15 km northwest of Skelleftea, Vasterbotten, Sweden.
  • In Finland, from near Kuortane, and in the Tammela district.
  • In the USA, giant crystals in the Etta mine, near Keystone, Pennington Co., and elsewhere in the Black Hills, South Dakota; at Hiddenite, Alexander Co. and in the Foote mine, Kings Mountain, Cleveland Co., North Carolina; from the Pala district, San Diego Co., California; and in the Harding mine, Dixon, Taos Co., New Mexico.
  • From the Tanco mine, Bernic Lake, Manitoba, Canada.
  • At the Urupuca mine, Itambacari, and at Resplendor, Minas Gerais, Brazil.
  • From Mawi and Kantiva, Nuristan district, Laghman Province, Afghanistan.
  • At Maharitra, Mt. Bity, and at Anjanabonoina, Madagascar.
  • From Bikita, Zimbabwe. Many other minor localities are known.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
  • Wikipedia contributors. (2019, March 21). Spodumene. In Wikipedia, The Free Encyclopedia. Retrieved 23:32, July 7, 2019, from https://en.wikipedia.org/w/index.php?title=Spodumene&oldid=888757472
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