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-.
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dollars for its apatite sale and deposit them in an escrow account.
The organoapatites are synthesized by nucleation and growth of apatite crystals in a media containing poly(amino acids) or synthetic organic polyelectrolytes using strict pressure, temperature, and pH controls.
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The minerals comprising the dykes include K-feldspar (microperthite), quartz, riebekite, biotite, muscovite, epidote, titanite, kaolin, apatite, zircon and limonite.
Gem-quality apatite is known from several localities.
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The presence of calcite, dolomite, silica (quartz, tridymite, cristobalite), apatite, clay minerals (smectite and smectite-illite) and rare sulfides in the matrix of natural OS, as well as in the IR of natural oil shale and burning test ash is interpreted from the results of XRD and SEM-EDS analyses.
Some trace elements have potential to expand the lattice parameters of the synthetic apatite crystal cell along the a-axis such as ferrous (Fe2+), ferric (Fe3+), strontium (Sr2+) and zinc ions (Zn2+) (molar fraction >10%) whereas it shrinks with silicate (SiO44-), carbonate (CO32-), magnesium (Mg2+), Zn2+ (molar fraction < 10%) and titanium ions (Ti4+).
John Bradshaw, Coast-to-Coast Rare Stones International, Nashua, New Hampshire, USA, for 21 bags containing part-cut crystals of: apatite (Canada and Mexico), cassiterite (Namibia), celestine (Kansas, USA), cerrusite (Namibia), crocoite (Tasmania, Australia), diaspore (Turkey), oligoclase (Kenya), pollucite (Conneticut, USA), scheelite (Pakistan and Arizona, USA), smithsonite (Namibia), sphalerite (Spain), tourmaline (Maine, USA, and Afghanistan), tugtupite (Greenland), willemite/leucophoenicite (New Jersey, USA) and zincite on calcite (New Jersey); and also for 95 faceted mixed-shape tourmalines, mostly pink, green and blue.
ACTIVA KIDS is an ionic restorative resin that stimulates mineral apatite formation and the natural remineralization process with release and recharge of calcium, phosphate and fluoride.