Apatite

Apatite is a mineral that is composed of calcium phosphate, with the chemical formula Ca5(PO4)3(OH,F,Cl). It is a member of the apatite group of minerals, which also includes hydroxylapatite and fluorapatite. Apatite is a relatively common mineral that can occur in a variety of colors, including yellow, green, blue, and purple. It is an important mineral in the formation of igneous, sedimentary, and metamorphic rocks, and it can also be found in biological tissues such as bones and teeth. Due to its chemical and physical properties, apatite has various industrial applications, including in the production of fertilizers, phosphoric acid, and dental materials.

It is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite

• Hydroxylapatite
• Fluorapatite
• Chlorapatite

Chemical composition of apatite

Apatite is a mineral with a relatively complex chemical composition, which can vary depending on the specific type of apatite. The basic formula for apatite is Ca5(PO4)3X, where X can be any one of several ions, including OH-, F-, Cl-, or a combination of these. Some variations in the formula can also occur due to the substitution of other elements for calcium or phosphorus.

The chemical composition of apatite can be further described by breaking down the individual components of the formula. The Ca5 component represents the calcium content of the mineral, which is an essential nutrient for many living organisms. The (PO4)3 component represents the phosphate content of the mineral, which is important for many industrial applications, including the production of fertilizers.

The X component of the formula represents the anion that can be present in apatite. If X is OH-, the mineral is called hydroxylapatite. If X is F-, the mineral is called fluorapatite. If X is Cl-, the mineral is called chlorapatite. If X is a combination of these anions, the mineral is called mixed-apatite.

In addition to the basic formula, apatite can also contain various trace elements and impurities, which can affect its properties and behavior. For example, rare earth elements such as lanthanum and cerium can substitute for calcium in the crystal structure of apatite, leading to variations in its physical and optical properties.

Apatite Physical Properties

• Color: Apatite can occur in a range of colors, including colorless, white, yellow, green, blue, purple, and brown. The color of apatite can be influenced by impurities or trace elements present in the mineral.
• Transparency: Apatite is usually transparent to translucent, although some varieties can be opaque.
• Crystal structure: Apatite has a hexagonal crystal structure, which means it has six-fold symmetry. Its crystal lattice is made up of repeating units of phosphate (PO4) tetrahedra and calcium (Ca) ions.
• Hardness: Apatite has a Mohs hardness of 5, which means it is relatively soft and can be easily scratched by harder minerals such as quartz.
• Cleavage: Apatite has a good cleavage in one direction, meaning it can be easily split along a flat plane.
• Fracture: Apatite has a conchoidal fracture, meaning it breaks with a smooth, curved surface similar to the way glass breaks.
• Luster: Apatite has a vitreous (glassy) luster, meaning it reflects light like glass.
• Density: The density of apatite varies depending on the composition of the mineral, but it typically falls between 3.1 to 3.4 g/cm³.

Apatite Optical Properties

• Refractive index: Apatite has a relatively high refractive index, ranging from 1.63 to 1.69. This means that light passing through apatite is bent or refracted at a greater angle than it would be in air.
• Birefringence: Apatite is strongly birefringent, meaning that it has two different refractive indices depending on the direction of light passing through it. This causes double refraction, where an object viewed through apatite appears to be split into two images.
• Pleochroism: Apatite exhibits pleochroism, which means that it can show different colors when viewed from different angles. This is due to the absorption of different wavelengths of light in different directions.
• Fluorescence: Some types of apatite exhibit fluorescence, meaning that they emit visible light when exposed to ultraviolet radiation. This property makes apatite useful in various applications such as in the production of fluorescent lamps.
• Optical dispersion: Apatite has a relatively high optical dispersion, which means that it can separate white light into its component colors or spectral lines. This property is used in gemological applications to identify different types of apatite and to distinguish them from other minerals.
• Absorption spectra: The absorption spectra of apatite can provide information on the mineral’s chemical composition and crystal structure. This property is used in various scientific and industrial applications, such as in geology to study the formation and evolution of rocks, and in medicine to analyze the chemical composition of bone tissue.
• Optical anisotropy: Apatite is optically anisotropic, meaning that it has different optical properties in different directions. This property is related to the mineral’s crystal structure, which has a hexagonal symmetry. The anisotropy of apatite can be used to determine the orientation and alignment of mineral grains in rocks, which can provide information on the geological history of the rocks.

Formation of Apatite

Apatite can form through several different geological processes, including igneous, sedimentary, and metamorphic processes. Here are some of the ways in which apatite can form:

• Igneous processes: Apatite can crystallize from magmas or melts that are rich in calcium and phosphorus. This often occurs in intrusive igneous rocks such as granite, syenite, and carbonatite. Apatite can also form in volcanic rocks such as basalt and andesite, where it can occur as phenocrysts or small crystals in the groundmass.
• Sedimentary processes: Apatite can be precipitated from aqueous solutions in sedimentary environments. This occurs when phosphate ions in solution react with calcium ions to form apatite crystals. Apatite can also be formed through the accumulation of biogenic material such as bone and teeth, which contain apatite.
• Metamorphic processes: Apatite can be formed through metamorphism, which occurs when rocks are subjected to high temperatures and pressures. During metamorphism, apatite can be recrystallized or transformed into different mineral phases, depending on the conditions of metamorphism.

Overall, the formation of apatite is closely linked to the availability of calcium and phosphorus, which are essential elements in the mineral’s chemical composition. The formation of apatite can provide important information on the geological history and processes that have affected rocks and minerals.

Geologic Occurrence

Apatite is a widely distributed mineral that can be found in various geological environments. Here are some of the common occurrences of apatite:

• Igneous rocks: Apatite is a common accessory mineral in igneous rocks such as granite, syenite, and carbonatite. It can occur as small crystals or grains, or as large masses or veins.
• Sedimentary rocks: Apatite can be found in sedimentary rocks such as phosphorites, which are rocks that are rich in phosphates. These rocks often form in marine environments where organic matter accumulates and decays, releasing phosphates into the surrounding water.
• Metamorphic rocks: Apatite can occur in metamorphic rocks such as marble, schist, and gneiss. During metamorphism, apatite can be recrystallized or transformed into different mineral phases, depending on the conditions of metamorphism.
• Hydrothermal veins: Apatite can be found in hydrothermal veins, which are mineralized fractures or fissures in rocks that are filled with mineral deposits. These veins can form in a variety of geological environments, including magmatic, metamorphic, and sedimentary rocks.
• Biological tissues: Apatite is an important component of bone and teeth, where it provides strength and hardness to these tissues. It can also be found in other biological materials such as fish scales and otoliths.

Overall, apatite occurs in a wide range of geological environments and can provide important information on the geological history and processes that have affected rocks and minerals. Its occurrence in biological tissues also makes it an important mineral in biology and medicine.

Distribution of apatite

Apatite is widely distributed throughout the world and can be found in a variety of geological settings. Here are some of the regions where apatite is commonly found:

• Canada: Canada is one of the world’s leading producers of apatite, with significant deposits located in Ontario, Quebec, and the Northwest Territories. These deposits occur in igneous and sedimentary rocks and are primarily mined for their phosphate content, which is used in fertilizer production.
• Russia: Russia is another major producer of apatite, with large deposits located in the Kola Peninsula in the far northwest of the country. These deposits occur in alkaline igneous rocks and are primarily mined for their phosphate content.
• Brazil: Brazil is home to significant apatite deposits, particularly in the state of Minas Gerais. These deposits occur in pegmatites and hydrothermal veins and are often associated with other rare minerals such as tourmaline and topaz.
• United States: Apatite deposits are found in several states in the United States, including Florida, Idaho, Tennessee, and Wyoming. These deposits occur in sedimentary rocks and are primarily mined for their phosphate content.
• Morocco: Morocco is home to some of the world’s largest apatite deposits, which occur in the Western Sahara and are primarily mined for their phosphate content.

Overall, apatite is widely distributed throughout the world and can be found in a variety of geological settings. Its importance in the production of fertilizer and other industrial applications has led to significant mining and extraction activities in many countries.

Uses of apatite

Apatite has a variety of uses in different fields, including industry, agriculture, and medicine. Here are some of the most common uses of apatite:

1. Fertilizers: Apatite is a major source of phosphate, which is a key nutrient required for plant growth. As a result, apatite is widely used in the production of fertilizers, particularly in the agricultural sector.
2. Industrial applications: Apatite is also used in various industrial applications, including the production of phosphate chemicals, such as phosphoric acid, which is used in the production of food additives, beverages, and detergents.
3. Ceramic industry: Apatite is used in the production of ceramics, such as dinnerware and decorative tiles, due to its high melting point and hardness.
4. Dental implants: Apatite is biocompatible, which means that it can be used in biomedical applications, such as dental implants and bone grafts.
5. Jewelry: Apatite is sometimes used as a gemstone due to its attractive colors, including blue, green, and yellow.
6. Research: Apatite is studied by researchers in geology, material science, and biology due to its unique properties, such as its crystal structure, optical properties, and chemical composition. Researchers use apatite as a model mineral for studying processes such as crystal growth, crystal chemistry, and biomimetics.

Overall, apatite is an important mineral with a wide range of applications, particularly in the agricultural and industrial sectors.

Phosphate Rock

Phosphate rock and phosphorite are names used for sedimentary rocks that contain at least 15% to 20% phosphate on the basis of weight. The phosphorous content in these rocks is mainly derived from the presence of apatite minerals

Uses of Apatite as Phosphate Rock

• Most of the phosphate rock mined throughout the world is used to produce phosphate fertilizer. It is also used to produce animal feed supplements, phosphoric acid, elemental phosphorous, and phosphate compounds for the chemical industry.
• China is the largest producer of phosphate rock, producing approximately 100 million tons in 2014. The United States, Russia, Morocco, and Western Sahara are also major phosphate producers.
• Over 75% of the world’s reserves of phosphate rock are located in Morocco and Western Sahara.

Apatite FAQ

What is apatite used for?

Apatite is used in various fields, including agriculture, industry, medicine, and research. It is a major source of phosphate, which is used in fertilizers, and it is also used in the production of phosphoric acid, ceramics, dental implants, and jewelry.

What are the physical properties of apatite?

Apatite is typically green, brown, blue, or yellow, and it has a hardness of 5 on the Mohs scale. It has a specific gravity of around 3.2 to 3.4, and it typically has a hexagonal crystal structure.

Where is apatite found?

Apatite is found in many locations around the world, including Canada, Brazil, Russia, and Madagascar. It can occur in a variety of geological environments, such as igneous rocks, sedimentary rocks, and hydrothermal veins.

Is apatite radioactive?

Some apatite can be radioactive, particularly if it contains trace amounts of uranium or other radioactive elements. However, not all apatite is radioactive, and its radioactivity can vary depending on the specific location and composition of the mineral.

What is the chemical composition of apatite?

Apatite has a complex chemical composition that can vary depending on the specific type of apatite. The basic formula for apatite is Ca5(PO4)3X, where X can be any one of several ions, including OH-, F-, Cl-, or a combination of these. Apatite can also contain various trace elements and impurities, which can affect its properties and behavior.

References

• Hobart M. King (2018) Apatite, Phosphorite and Phosphate Rock https://geology.com/minerals/apatite.shtml
• Market Price , https://roughmarket.com/apatite/
• Arem,J,E.,Smigel,B (2018) Apatite Value, Price, and Jewelry Information, International Gem Society
• Villalba,G.,Ayres, R,U.,Schroder, H(2008). “Accounting for Fluorine: Production, Use, and Loss”. Journal of Industrial Ecology.
• USGS, Mineral commodity summaries, Available at http://minerals. usgs.gov/minerals/pubs/commodity/phosphate_rock/index.html#mcs verified 19 April 2013).