Madagascar apatite

Category: Phosphate mineral group

 

Chemical formula: Ca5(PO4)3(F,Cl,OH)

 

Strunz classification: 08.BN.05

 

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

 

Mohs scale hardness: 5[1] (defining mineral)

 

Luster: Vitreous[1] to subresinous

 

Specific gravity: 3.16–3.22

 

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