Fluorapatite



Fluorapatite

General
CategoryPhosphate mineral
Chemical formulaCa5(PO4)3F
Identification
ColorSea-green, violet, purple, blue, pink, yellow, brown, white, colorless, may be zoned
Crystal habitMassive to prismatic cyrstaliine
Crystal systemHexagonal - dipyramidal
TwinningContact twins rare
CleavageIndistinct
FractureBrittle to conchoidal
Mohs Scale hardness5
LusterVitreous, resinous to dull
Refractive indexnω = 1.631 - 1.650 nε = 1.633 - 1.646
Optical PropertiesUniaxial (-)
Birefringenceδ = 0.002
Ultraviolet fluorescenceFluorescent and phosphorescent.
StreakWhite
Specific gravity3.1 to 3.2
DiaphaneityTransparent to Opaque
References[1][2][3]

  Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca5(PO4)3F (calcium halophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. It is an important constituent of tooth enamel.[4]

Fluorapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca5(PO4)3OH) in biological matrices. Chloroapatite (Ca5(PO4)3Cl) is another related structure.[4]

Fluorapatite is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.[1]

Synthesis

Fluorapatite can be synthesized in a two step process. First, phosphorus cycle.[5]

3Ca2+ + 2PO43- → Ca3(PO4)2
3 Ca3(PO4)2 + CaF2 → 2 Ca5(PO4)3F

Fluorapatite can also be used as a precursor for the production of white phosphorus, P4:

Ca5(PO4)3F + 3SiO2 + 5C → 3CaSiO3 + 5CO + P2

2P2 → P4 after cooling.

References

  1. ^ a b http://rruff.geo.arizona.edu/doclib/hom/fluorapatite.pdf Mineral Handbook
  2. ^ http://webmineral.com/data/Fluorapatite.shtml Webmineral
  3. ^ http://www.mindat.org/min-1572.html Mindat
  4. ^ a b Hurlbert and Klein. "Manual of Mineralogy, 19th Edition". 1977. ISBN 0471251771
  5. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Fluorapatite". A list of authors is available in Wikipedia.