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Apatite

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH, F and Cl ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca( PO)(OH,F,Cl), and the crystal unit cell formulae of the individual minerals are written as Ca(PO)(OH), Ca(PO)(F) and Ca(PO)(Cl).

The mineral was named apatite by the German geologist Abraham Gottlob Werner in 1786, although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German mineralogist Karl Friedrich August Rammelsberg. Apatite is a mineral that is often mistaken for other minerals. This tendency is reflected in the mineral's name, which is derived from the Greek word απατείν (apatein), which means to deceive or to be misleading.

Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material.

Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite; in the mid-20th century, it was discovered that communities whose water supply naturally contained fluorine had lower rates of dental caries. Fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate). Too much fluoride results in dental fluorosis and/or skeletal fluorosis.

Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins. (U-Th)/He dating of apatite is also well established for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating.

Phosphorite is a phosphate-rich sedimentary rock, that contains between 18% and 40% PO. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane.

The Collaborative International Dictionary

Apatite

Apatite \Ap"a*tite\, n. [Gr. ? deceit, fr. ? to deceive; it having been often mistaken for other minerals.] (Min.) Native phosphate of lime, occurring usually in six-sided prisms, color often pale green, transparent or translucent.

Wiktionary

apatite

n. (context mineral English) A calcium fluoride phosphate of variable composition, sometimes used in the manufacture of fertilizer.

WordNet

apatite

n. a common complex mineral consisting of calcium fluoride phosphate or calcium chloride phosphate; a source of phosphorus

Usage examples of "apatite".

Inside the wet tissues of the body, the two chemicals react, and they precipitate hydroxyl apatite, a tough, rigid, natural constituent of actual human bone.

They located two roads, neither passable by now, one track leading to a shallow pit where many tons of apatite had been removed.

Canada it occurs with apatite in pyroxene rocks which are intrusive in Laurentian gneisses and crystalline limestones, the principal mining district being in Ottawa county in Quebec and near Burgess in Lanark county, Ontario.

Kemjawi as a byproduct of feldspar mining, and phlogopite at Siilinjarvi from an apatite mine.