apatite

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apatite

(ăp`ətīt), mineral, a phosphate of calcium containing chlorine or fluorine, or both, that is transparent to opaque in shades of green, brown, yellow, white, red, and purple. Apatite is a minor constituent in igneous and metamorphic rocks. Yellow-green asparagus stone and blue-green manganapatite are used in jewelry. Apatite is mined to make phosphatic fertilizers and is used in fission track dating of rocks (see datingdating,
the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute.
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). Commercial deposits are mined in Idaho, Tennessee, and Wyoming, and in N Africa and Russia.

Apatite

 

a mineral of the calcium phosphate group containing a variable quantity of fluorine and chlorine. The chemical formula of apatite is 3Ca3 (PO4) 2·Ca(F, Cl)2. As secondary admixtures apatite sometimes contains up to 10 percent oxides of manganese, strontium, or rare earth elements; less than 1 percent sodium, potassium, or barium frequently replaces part of the calcium. In addition to F- and Cl-, (OH)-, O2-, and CO32-, are also present. Fluor-, chlor-, hydroxyl-, carbonate-, and oxy-apatite have been isolated, as have been manganapatite, strontium apatite, and rare earth apatite (“belovit”). The theoretical composition P2O5 in fluorapatite and chlorapatite is 42.3 percent and 41.1 percent respectively. Apatite crystallizes in a hexagonal system. Crystals are for the most part hexahedral, prismatic, and elongated to the point of being needlelike; they are rarely tabular. Apatite is also found in the form of cryptocrystalline varieties (col-lophanite). The color and other physical and optical properties change within the bounds of the series of fluor-, chlor-, and hydroxylapatite as well as according to the composition of the admixtures of elements. The green color of apatite is caused by the presence of iron, its blue color by manganese, and its brown and red color by a finely dispersed admixture of hematite. Its cleavage is incomplete; its luster is vitreous and resinous; its hardness on the mineralogical scale is 5; and its density ranges from 3,160 to 3,200 kg/m3 but reaches 3,800–4,200 kg/m3 in varieties enriched with strontium and the rare earths. The melting point is 1660°C for fluorapatite and 1530°C for chlorapatite.

Apatite is widely distributed in rocks and is formed by various geological processes. Large apatite ore accumulations are confined to massive alkaline rocks (nepheline syenites). A high apatite content has also been established in carbonatites and in certain iron ore deposits formed at high temperatures. In addition, apatite is found in granite, pegmatites, quartz veins, crystalline schists. In sedimentary rocks, minerals of the apatite group occur mainly in the form of phosphorites and partly in excavated bones. Because of its relative chemical stability, apatite is found in placers.

Most of the apatite which is mined is utilized in the manufacture of phosphorous fertilizers. In the chemical industry apatite yields phosphoric acid, various salts, phosphorus, and phosphorous compounds. Apatite is also used in ferrous and nonferrous metallurgy and in the ceramic and glass industries.

The world’s largest deposit of apatite is found in the USSR on the Kola Peninsula. Abroad, the largest deposits of apatite are found in the iron ore fields of Sweden (Kierunavaara, Luossavaara) and in the carbonatóte fields of central and eastern Africa.

REFERENCES

Bok, I. I. Agronomicheskie rudy, 2nd ed. Alma-Ata, 1965.
Deer, W. A., R. A. Howie, and J. Zussman. Porodoobrazuiushchie mineraly, vol. 5. Moscow, 1966. (Translated from English.)

A. M. PORTNOV

apatite

[′ap·ə‚tīt]
(mineralogy)
A group of phosphate minerals that includes 10 mineral species and has the general formula X5(YO4)3Z, where X is usually Ca2+or Pb3+, Y is P5+or As5+, and Z is F-, Cl-, or OH-.
References in periodicals archive ?
It can be seen that the samples have been covered by apatite cell since first day Fig.
SBF study is a primary and an essential test to establish the biocompatibility of the developed material, where the formation of apatite on the nanocomposites is to be confirmed.
Single or ordinary superphosphate (SSP about 9% P) was the first water-soluble P fertilizer to be manufactured on large scale by reaction of apatite phosphate rock with sulphuric acid.
RPs from Egypt, Morocco, North Carolina, and Sechura contain francolite (carbonate apatite) as the major apatite mineral, while Queensland and Christmas Island A-ore contain fluorapatite.
The aim of this work is to use REE geochemistry of fossil vertebrate apatite in an attempt to reveal the palaeoenvironmental conditions and depositional history of the Vesiku Bone Bed, and by inference, provide insights into vertebrate palaeoecology.
There are two main groups, he says, those that can accumulate increased amounts of rare earth elements in their structure--garnets, zircons, apatites, and perovskites--and those whose structure can accumulate only limited contents of these trace minerals--chrome-spinels, ilmenites, and micas.
Synthesized doped apatites were crushed to fine powder and then subjected to calcination at different four temperatures.
Following an overview of the field, papers describe recent methodological advances, including an automated counting system for fission tracks in natural minerals, the use of laser ablation inductively coupled plasma mass spectrometry for measuring uranium concentration for apatite and zircon fission-track chronometry, and detrital thermochronology based on measuring Nd isotopic compositions on single apatites by laser ablation ICP-MS, to cite a few examples.