Apatite

Apatite ( apatite ) is the short - and collective name for a group of chemically similar, but not closer to certain minerals with the following members:

Apatite is also namesake of the apatite - pyromorphite group with high (up to 100 %) and freely exchangeable concentration of simple negative fluorine, chlorine or hydroxide ions. The general chemical formula for apatite Ca5 [( F, Cl, OH ) | ( PO4 ) 3].

All minerals are minerals class of " phosphates, arsenates, and vanadates " and crystallize in the hexagonal crystal system with the general chemical composition ( Ca, Ba, Pb, Sr, etc.), 5 [ (F, Cl, OH ) | ( PO4, CO3 ) 3] and develop mostly tabular to prismatic crystals, but also low one to grape-like, spherical, granular, fibrous and massive mineral aggregates and stalagmite forms and crusty coatings of variable, but often green, brown or white color.

With a Mohs hardness of 5 apatites are among the medium-hard minerals that can be scratched with the knife still. They are used in the same hardness scale as a reference mineral. Depending on the composition of the apatites have a density of 3.1 g/cm3 to 3.8.

Etymology

The name apatite is derived from the ancient Greek άπατᾶν ápatân "fool " from. Since the mineral in so many shapes and color variations occur, the risk is great that it is confused with the minerals such as beryl, topaz or different tourmalines.

Individual minerals and varieties

• Fluorapatite - very common occurrence, either colorless or white, yellow, pink, blue, purple, green, brown
• Chloroapatite - rather rare occurrence in white or shades of yellow
• Hydroxyapatite - rather rare occurrence in the colors white, various shades of gray or yellow
• Apatite Cat's Eye
• Asparagus stone - yellowish- green
• Mangualdit - manganese-containing apatite
• Moroxit - bluish- green, purple, red

Education and Locations

Hydrothermal apatite occurs in pegmatites and metamorphic limestone, but is also found in igneous rock or organic material in sedimentary rocks. Frequently caused by apatites biomineralization, whether in rock formations, in the base, as an undesired plaque, bone, etc.; here but always in very specific micro - environmental conditions.

Locations include Brazil, the People's Republic of China, India, Clear Lake / Ontario in Canada, Madagascar, Morocco, Mercado and Durango in Mexico, Myanmar (Upper Burma), Dusso in Pakistan, Kola Peninsula in the Russian Federation, Fiesch in Switzerland, Sri Lanka, Maine in the United States.

Synthesis

Hydroxyapatite is synthesized by the Tiselius method:

For this purpose, in the first step of calcium chloride ( CaCl2) and disodium hydrogen phosphate ( Na2HPO4 ), the compound brushite (calcium hydrogen phosphate dihydrate, CaHPO4 · 2H2O ) were prepared. The very poorly water soluble brushite is then boiled in caustic soda (NaOH ) until it has been transformed into hydroxyapatite.

Biological Importance and Uses

In living organisms

Hydroxyapatite is an important building block in the construction of bone tissue. Osteoblasts are capable of producing the mineral of phosphate and calcium ions and hydroxyapatite variable installed in the bone. For example, the bones of the body skeleton consist of about 50%, the dentin ( dentin ) of about 70 % and about 97% of dental enamel hydroxyapatite. In kidney stones proportions may be comprised of apatite.

As a raw material

• Apatite is an important ore for the recovery of phosphorus and thus for the production of fertilizers and phosphoric acid for the chemical industry.
• In medicine, the variety is as hydroxyapatite artificial bone substitute ( engl. "bone graft" ), partly used in combination with calcium phosphate, or as bioactive coating of titanium implants to improve the bone replacement.
• Hydroxyapatite used in the chromatographic separation of proteins as a stationary phase in the column.

As a gemstone

Increasingly, apatites in the jewelry industry of significance, particularly jewelry stones with cat's eye effect. However, processing by the high sensitivity to acid and heat supply is difficult. Color changes are possible even at low heat or strong light.