Apatite - Ca5(PO4)2[F, OH, Cl]

Apatite structure is characterized by phosphate oxyanion linked by Ca2+ cations to forma hexagonal frame-work with F- anions lying at the corners of hexagonal cell and coordinated by three Ca2- cations. Composition of the apatite minerals is highly variable and there is a complete solid solution between three end-members, fluoroapatite Ca5(PO4)3F, chloroapatite Ca5(PO4)3Cl and hydroxylapatite Ca5(PO4)OH. The dominant anion (F,Cl,OH) determinate the Apatite variety.
Apatite is a very common early-formed accessory mineral in nearly all type of igneous rocks. Apatite is also concentrated by late magmatic segregation, and it appears in granite pegmatite.

Optical Properties:

Form: Tiny euhedral prismatic crystals elongated on c, with exagonal basal section and rectangular to acicular prismatic section.
Relief: High.
Color: Colorless.
Interference Colors: weak.
cleavage: Poor parallel to (001).


apatite2017.jpg

Cristalli verdi di apatite in una carbonatite. Siilinjärvi, Finlandia. Immagine tratta da sand atlas.




Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc


Photo
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals in Biotite. PPL image, 2x (Field of view = 7mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. XPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals (hexagonal basal section) in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals in Augite. XPL image, 10x (Field of view = 2mm)
nefelinolite2014)(37).jpg

Apatite crystals in Augite. PPL image, 10x (Field of view = 2mm)
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Apatite crystals in Augite. PPL image, 10x (Field of view = 2mm)