Apatite



Not to be confused with appetite, the desire to eat.
Apatite

General
CategoryPhosphate mineral group
Chemical formulaCa5(PO4)3(F,Cl,OH)
Identification
ColorTransparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown.[1]
Crystal habitTabular, prismatic crystals, massive, compact or granular
Hexagonal Dipyramidal (6/m)[2]
Cleavage[0001] Indistinct, [1010] Indistinct[2]
FractureConchoidal to uneven[1]
Mohs Scale hardness5[1]
LusterVitreous[1] to subresinous
Polish lusterVitreous[1]
Refractive index1.634 - 1.638 (+.012, -.006)[1]
Optical PropertiesDouble refractive, uniaxial negative[1]
Birefringence.002-.008[1]
Dispersion.013[1]
PleochroismBlue stones - strong, blue and yellow to colorless. Other colors are weak to very weak.[1]
Ultraviolet fluorescenceYellow stones - purplish pink which is stronger in long wave; blue stones - blue to light blue in both long and short wave; green stones - greenish yellow which is stronger in long wave; violet stones - greenish yellow in long wave, light purple in short wave.[1]
StreakWhite
Specific gravity3.16 - 3.22[2]
DiaphaneityTransparent to translucent[2]

Apatite is a group of minerals are written as Ca5(PO4)3(OH), Ca5(PO4)3F and Ca5(PO4)3Cl, respectively.

Apatite is one of few minerals that are produced and used by biological micro-environmental systems. Hydroxylapatite is the major component of tooth enamel. 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.

skeletal fluorosis.

In the United States, apatite is often used to fertilize tobacco. It partially starves the plant of nitrogen, which gives American cigarettes a different taste from those of other countries.

Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins.

Phosphorite is the name given to impure, massive apatite.

Gemology

Apatite is infrequently used as a moroxite.[3] 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[1] Brazil, Burma, and Mexico. Other sources include[1] Canada, Czechoslovakia, Germany, India, Madagascar, Mozambique, Norway, South Africa, Spain, Sri Lanka, and the US.

See also

 

References

  1. ^ a b c d e f g h i j k l m n o p Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
  2. ^ a b c d http://webmineral.com/data/Apatite.shtml Webmineral data
  3. ^ Streeter, Edwin W., Precious Stones and Gems 6th edition, George Bell and Sons, London, 1898, p306
  • Apatite on Mineral galleries

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.
 
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