Blue apatite

General

Category: Phosphate mineral

Formula: Ca5(PO4)3(F,Cl,OH)

Strunz classification: 8.B

Crystal system: Hexagonal


Identification

Color: Transparent - translucent, usually green, less often colorless, yellow, blue to violet, pink, brown.

Crystal habit: Tabular, prismatic crystals, massive, compact or granular

Cleavage: [0001] indistinct, [1010] indistinct

Mohs scale hardness: 5

Luster: Vitreous to subresinous

Streak: White

Diaphaneity: Transparent to translucent

Specific gravity: 3.16–3.22

Polish luster: Vitreous

Optical properties: Double refractive, uniaxial negative

Refractive index: 1.634–1.638 (+0.012, −0.006)

Birefringence: 0.002–0.008

Pleochroism: Blue stones – strong, blue and yellow to colorless. Other colors are weak to very weak

Dispersion: 0.013


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