Kyanite

Kyanite is a mineral composed of aluminum silicate, and it belongs to the family of aluminosilicate minerals. Its chemical formula is Al2SiO5. Kyanite typically forms bladed crystals, and its name is derived from the Greek word “kuanos,” meaning blue, which reflects its most common blue coloration.

Name: From the Greek for blue, in allusion to its common dark blue color.

Type Material: Mining Academy, Freiberg, Germany, 22491.

Association: Staurolite, andalusite, sillimanite, talc, \hornblende,” gedrite, mullite, corundum.

Formation and Occurrence

The formation and occurrence of kyanite are closely linked to the geological processes associated with regional metamorphism. Kyanite is primarily found in metamorphic rocks, and its formation involves specific conditions. Here’s an overview of how kyanite forms and where it is commonly found:

Formation:

Kyanite is formed under high-temperature, high-pressure conditions, which are characteristic of regional metamorphism. The following are the key steps in its formation:

1. Parent Rocks: Kyanite typically originates from pre-existing minerals in sedimentary or igneous rocks. The parent rocks could be rich in aluminum and silica, such as clay-rich sedimentary rocks or aluminum-rich igneous rocks.
2. Increased Temperature and Pressure: These parent rocks undergo tectonic processes that subject them to increased temperature and pressure. This is often due to the burial of rocks deep within the Earth’s crust during mountain-building events or the collision of tectonic plates.
3. Mineral Transformation: Under these extreme conditions, the minerals in the parent rocks start to undergo metamorphic changes. In the case of kyanite, aluminum silicate minerals in the parent rocks transform into kyanite. This transformation involves the rearrangement of atoms to form the characteristic bladed crystals of kyanite.
4. Recrystallization: Kyanite crystals grow as the minerals recrystallize, and they often align themselves along preferred orientations. This alignment is a result of the foliation or preferred orientation of minerals in metamorphic rocks.

Occurrence:

Kyanite is typically found in metamorphic rocks, and it occurs in a variety of geological settings. Here are some common locations where kyanite can be found:

1. High-Grade Metamorphic Rocks: Kyanite is often associated with high-grade metamorphic rocks, such as schists and gneisses. These rocks are subjected to extreme temperature and pressure conditions, making them ideal environments for kyanite formation.
2. Mountain Ranges: Kyanite is frequently discovered in mountainous regions, where intense tectonic activity and mountain-building processes have caused the deep burial and metamorphism of rocks. For example, the Himalayas, the Appalachian Mountains, and the Alps are known areas for kyanite occurrences.
3. Mineral Associations: Kyanite is commonly found alongside other metamorphic minerals, including staurolite, garnet, and andalusite. These minerals often occur together in the same rock types.
4. Specific Geological Zones: In some cases, kyanite-bearing rocks are concentrated in specific geological zones or formations. Geologists may explore these areas to study the mineral’s occurrences and potential uses.

It’s important to note that kyanite’s occurrence can vary in color and quality based on the specific geological conditions in which it forms. While blue kyanite is the most well-known variety, it can also be found in other colors, including green, gray, white, and even colorless. The presence of impurities or different chemical compositions can influence its coloration.

In summary, kyanite is primarily formed through the metamorphism of aluminum-rich minerals in high-pressure, high-temperature environments within the Earth’s crust. It is commonly associated with specific types of metamorphic rocks and is often found in regions with a history of mountain-building and tectonic activity.

Physical Properties of Kyanite

Chemical Classification	Silicate
Color	Blue, white, gray, green, colorless
Streak	White, colorless
Luster	Vitreous, pearly
Diaphaneity	Transparent to translucent
Cleavage	Perfect in two directions, faces sometimes striated
Mohs Hardness	Kyanite often occurs in long, bladed crystals. These have a hardness of 4.5 to 5 along the length of the crystals and 6.5 to 7 across the width of the crystals.
Specific Gravity	3.5 to 3.7
Diagnostic Properties	Color, cleavage, bladed crystals
Chemical Composition	Al2SiO5
Crystal System	Triclinic
Uses	Ceramics, gemstones

Optical Properties of Kyanite

Property	Value
Formula	Al2SiO5
Crystal System	Triclinic
Crystal Habit	Elongate or columnar crystals in bladed aggregates
Cleavage	Perfect cleavage on (100) and good cleavage on (010) intersect at 79°
Color/Pleochroism	Pale blue in hand samples.  Colorless to light patchy blue in thin section.  Weak pleochroism in thin section where X= colorless, Y= light violet blue, and Z= light cobalt blue
Optic Sign	Biaxial (-)
2V	78°-84°
Optic Orientation	Z: inclined 27° – 32° to the c axis Y: inclined 27° – 32° to the b axis X: inclined a few degrees to the a axis
Refractive Indices alpha = beta = gamma = delta =	1.710-1.718 1.719-1.725 1.724-1.734 0.012-0.016
Elongation	Prismatic crystals and cleavage fragments are length slow
Extinction	Inclined (see optic orientation).
Dispersion	Weak r > v
Distinguishing Features	Colorless and dark in thin section with high positive relief! Second-order interference colors. Two prominent, high angle cleavages occur parallel and perpendicular to the length of the crystal blades. Hardness = 4-5 parallel to c and 7.5 at right angles to c. G = 3.53 to 3.67. Streak is white. Luster is vitreous.
References	Nesse, William D. (2000) Introduction to mineralogy. New York: Oxford University Press. Nesse, William D. (1986) Introduction to optical mineralogy. New York: Oxford University Press.
Editors	Wendy Kelly (’05), Rhiannon Nolan (’19)

Varieties of Kyanite

Kyanite occurs in various colors and types, each with unique characteristics and, sometimes, distinct metaphysical properties. Here are some of the notable varieties of kyanite:

1. Blue Kyanite: Blue kyanite is the most well-known variety and is prized for its vibrant blue color. It is often used in jewelry, and its metaphysical properties are believed to promote communication, self-expression, and psychic abilities. Blue kyanite is thought to align and clear the throat and third-eye chakras.
2. Green Kyanite: Green kyanite is known for its green or bluish-green coloration. It is believed to enhance connection with nature and the environment. Green kyanite is associated with the heart chakra and is said to aid in healing, balance, and growth.
3. Black Kyanite: Black kyanite is characterized by its dark color, ranging from black to deep gray. It is believed to have grounding and protective properties, helping individuals connect with the Earth’s energies. Black kyanite is often used in meditation and energy work to clear blockages and negative energy.
4. Orange Kyanite: Orange kyanite is associated with the sacral chakra and is believed to stimulate creativity, sociability, and self-esteem. It is thought to have a warming and energizing effect on the individual. The color may range from pale orange to reddish-orange.
5. Auralite-23: Auralite-23 is a rare type of kyanite that is characterized by its unique combination of more than 23 different minerals, including kyanite, amethyst, and various other crystals. It is believed to possess powerful metaphysical properties, promoting spiritual growth, insight, and healing. Auralite-23 is often used in meditation and energy work.
6. Rainbow Kyanite: Rainbow kyanite is a variety that exhibits multiple colors within the same crystal. It may display bands or streaks of various hues, often in shades of blue, green, and gray. Rainbow kyanite is thought to balance and align the chakras, harmonizing energies within the body.
7. Yellow Kyanite: Yellow kyanite is less common but can be found in some locations. It is associated with the solar plexus chakra and is believed to enhance one’s personal power, confidence, and clarity. Yellow kyanite may range from pale yellow to golden yellow.
8. Pink Kyanite: Pink kyanite is a rarer variety and is characterized by its delicate pink color. It is associated with the heart chakra and is believed to promote love, compassion, and emotional healing. Pink kyanite is used in metaphysical practices to enhance emotional balance.

These different varieties of kyanite are often used in crystal healing, meditation, and energy work, where each variety is thought to have specific properties that can influence the individual’s energy and well-being. It’s important to note that the metaphysical properties of kyanite are based on esoteric beliefs and not scientifically proven, so their effects are a matter of personal belief and interpretation.

Uses and Application of Kyanite

Kyanite is a versatile mineral with a range of practical and industrial applications due to its unique properties, particularly its high refractoriness, anisotropy, and resistance to heat and wear. Here are some of the primary uses and applications of kyanite:

1. Refractory Materials: Kyanite is primarily used as a raw material in the production of high-temperature refractory materials. Its high melting point and resistance to thermal shock make it ideal for manufacturing refractory bricks, castables, and other products used in high-temperature environments such as furnaces, kilns, and glass manufacturing.
2. Kiln Linings: Kyanite’s ability to withstand extremely high temperatures makes it suitable for lining industrial kilns and ovens. It helps maintain the integrity of these structures in applications like ceramic production and the firing of metals.
3. Foundry Industry: Kyanite is used in the foundry industry as a component in the production of foundry molds. It helps create molds that can withstand the high temperatures and thermal cycling during metal casting.
4. Glass Manufacturing: Kyanite is added to glass formulations to enhance the quality and durability of high-temperature glass products, such as fiberglass and laboratory glassware. It helps improve the resistance of glass to thermal stress.
5. Abrasives: In some cases, kyanite can be used as an abrasive material. Its hardness and durability make it suitable for abrasive applications like grinding wheels, cutting tools, and sandpaper. However, it is less common in abrasives compared to other minerals like corundum (aluminum oxide).
6. Ceramics: Kyanite is used in the production of ceramics, particularly in the creation of porcelain and fine china. It improves the strength and thermal resistance of these products, allowing them to withstand high-temperature firing processes.
7. Metallurgical Industry: Kyanite can be utilized in the metallurgical industry as a refractory material for lining furnaces and crucibles used in the smelting and refining of metals, including steel, aluminum, and non-ferrous metals.
8. Jewelry: Blue kyanite, with its attractive blue color and unique crystal habit, is sometimes used in jewelry as cabochons, faceted gemstones, and decorative beads. However, it is less commonly used in jewelry compared to other gemstones due to its relatively low hardness.
9. Metaphysical and Healing Uses: Kyanite is believed by some to possess metaphysical properties that aid in energy work, meditation, and chakra alignment. It is thought to promote communication, self-expression, and healing.
10. Indicator Mineral in Geological Studies: Geologists use the presence of kyanite in metamorphic rocks as an indicator mineral to gain insights into the geological history and conditions of the region where it is found. The presence of kyanite can provide information about the temperature and pressure at which the rocks formed.

Kyanite’s use in these applications is largely due to its exceptional refractory properties and resistance to heat and wear. It plays a crucial role in various industries where materials must withstand extreme conditions, and its diverse colors and varieties add to its appeal for collectors, jewelry makers, and those interested in metaphysical practices.

Mining and Distribution of Kyanite

Kyanite is primarily obtained through mining, and its distribution is influenced by geological factors, as well as market demand. Here’s an overview of the mining and distribution of kyanite:

Mining of Kyanite:

1. Location: Kyanite is typically found in regions with metamorphic rock formations. It is often associated with schists, gneisses, and other high-grade metamorphic rocks. The presence of kyanite is indicative of the high-temperature and high-pressure conditions that exist in these areas.
2. Extraction: Kyanite is extracted from quarries and mines. The mining process involves drilling, blasting, and excavation to access kyanite-bearing ore bodies. Miners must be cautious during extraction to preserve the quality of the kyanite crystals.
3. Sorting and Processing: After extraction, the kyanite-bearing ore is transported to processing facilities. There, the ore is crushed, sorted, and often subjected to gravity separation methods to concentrate the kyanite. It is then further processed to remove impurities and improve the mineral’s quality.
4. Grades and Varieties: Kyanite comes in various grades, depending on its color, quality, and intended use. High-quality kyanite with intense blue color is typically more valuable, while lower-grade or green kyanite may be used in different applications.

Distribution of Kyanite:

1. Global Distribution: Kyanite is found in various parts of the world, with significant deposits located in several countries. Some of the notable regions for kyanite mining and distribution include:
   • United States: The United States, particularly the states of Georgia, North Carolina, and Virginia, has been a historically significant producer of kyanite. These states contain deposits of high-quality blue kyanite.
   • Brazil: Brazil has been another prominent source of kyanite, known for its blue and green varieties.
   • Nepal: Nepal is known for its high-quality blue kyanite deposits, often found in the Daha area.
   • India: Kyanite is also mined in India, particularly in the states of Jharkhand and Orissa.
   • Switzerland: Switzerland has yielded kyanite from the Zermatt region, and Swiss kyanite is known for its transparent crystals.
   • Australia: Kyanite is found in parts of Australia, such as New South Wales.
   • Myanmar (Burma): Myanmar is another source of kyanite, with both blue and green varieties.
2. Market Demand: The distribution of kyanite can also be influenced by market demand. In regions with industries that require high-temperature refractory materials, there may be increased mining and distribution of kyanite to meet these industrial needs.
3. Gem and Jewelry Trade: Some kyanite, especially the blue and transparent varieties, is distributed through the gem and jewelry trade. Gem dealers and jewelry manufacturers source kyanite for use in gemstone jewelry, cabochons, and faceted gemstones.

It’s worth noting that kyanite is not as widely distributed as some other minerals, and its presence is closely tied to specific geological conditions. Therefore, its availability and production levels can fluctuate depending on the economics of mining, market demand, and the geological characteristics of the regions where it is found.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].