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

 

Done