Apatite

{{Infobox mineral | name = Apatite | category = Phosphate mineral group | boxwidth = | boxbgcolor = | image = Apatite crystals.jpg | imagesize = | caption = | formula = Ca₅(PO₄)₃(F,Cl,OH) | molweight = | strunz = 08.BN.05 | color = Transparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown. | habit = Tabular, prismatic crystals, massive, compact or granular | system = Hexagonal Dipyramidal (6/m) | twinning = | cleavage = [0001] Indistinct, [1010] Indistinct

In the United States, apatite derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a valuable source of phosphate.

Gemology

Apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon cut. Crystals of rutile may have grown in the crystal of apatite so when in the right light, the cut stone displays a cat's eye effect. Major sources for gem apatite are This is preferable to traditional rare earth ores, as apatite is non-radioactive and does not pose an environmental hazard in mine tailings.

Apatite is an ore mineral at the Hoidas Lake rare earth project.

Thermodynamics

The standard (p = 0.1 MPa) molar enthalpies of formation in the crystalline state of hydroxyapatite, chlorapatite and a preliminary value for bromapatite, at T = 298.15 K, have already been determined by reaction-solution calorimetry. Speculations on the existence of a possible fifth member of the calcium apatites family, iodoapatite, have been drawn from energetic considerations.

Lunar science

Moon rocks collected by astronauts during the Apollo program contain traces of apatite. Re-analysis of these samples in 2010 revealed water trapped in the mineral as hydroxyl, leading to estimates of water on the lunar surface at a rate of at least 64 parts per billion – 100 times greater than previous estimates – and as high as 5 parts per million. If the minimum amount of mineral-locked water was hypothetically converted to liquid, it would cover the Moon's surface in roughly one meter of water.

See also

List of minerals

Thermal history modelling

Hexafluorosilicic acid

References

Further reading

Schmittner Karl-Erich and Giresse Pierre, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463–476.

Category:Calcium minerals Category:Phosphate minerals Category:Gemstones Category:Halide minerals Category:Piezoelectric materials Category:Hexagonal minerals