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Apatite

A natural, variously colored calcium fluoride phosphate, Ca₅F(PO₄)₃, with chlorine, hydroxyl, or carbonate sometimes replacing the fluoride. It is a source of phosphorus for plants and is used in the manufacture of fertilizers.

Apatite occurs in nearly every rock type as an accessory mineral. It often crystallizes in regional and contact metamorphic rocks, especially in limestone and associated with chondrodite, which is the most common and most well known member of the Humite Group of minerals and phlogopite, which is a yellow to dark brown mica, K(Mg,Fe)AlSiO(OH), used in insulation. It is very common in basic to ultrabasic rocks; enormous masses occur associated with nepheline syenites in the Kola Peninsula, Russia, and constitute valuable ores which also contain rare-earth elements. Large beds of oolitic(like a small round calcareous grain found, for example, in limestones), pulverulent, and compact fine-grained carbonate-apatites occur as phosphate rock, phosphorites(sedimentary rocks consisting predominantly of apatite and other phosphates), or collophanes(the apatite in fossil bone and phosphate rock belongs to the series). Extensive deposits of this kind occur in the United States in Montana and Florida and in North Africa. The material is mined for fertilizer and for the manufacture of elemental phosphorus.

Material Notes:
Calcium hydroxyapatite is a natural constituent of teeth and bone, along with other calcium-phosphate ceramic (CPC) materials. Synthetic hydroxyapatite is used as an active bioceramic for teeth and bone replacement. Ionic substitution is common and plays a large role in the structure and properties of hydroxyapatites.

Apatite may be regarded as a single mineral, but is usually divided into three more minerals: Fluorapatite, Chlorapatite, and Hydroxylapatite(hydroxyapatite, the principal bone salt, Ca(PO)OH, which provides the compressional strength of vertebrate bone). Since it is hard to distinguish between these minerals, and since they may partially replace each other, a distinction between them is rarely made, and they are simply called "Apatite". However, most Apatite is Fluorapatite, the most common member by far.

Apatite is the most common phosphate mineral, and is the main source of the phosphorus required by plants. The bones and teeth of most animals, including humans, are of the same material as Apatite.

Apatite is named from the Greek word apate, which means "deceit", since Apatite has a similar appearance to so many minerals.

Apatite is a common mineral, and fine localities are worldwide. Enormous deposits are in the Kola Peninsula, Russia, containing both crystals and botryoidal material. Some of the finest crystals came from Ehrenfriedersdorf, Saxony Germany, where they are blue to purple in color. Colorless, hexagonal crystals were found in the Tyrol, Austria, and excellent material from Panasqueira, Portugal. Deep blue crystals are found in Campo Formosa, Bahia, Brazil, and in Sri Lanka. Enormous deposits mined for industrial use exist in Nauru, Morocco, Algeria, Tunisia, Egypt, and Israel.

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