neil cohen, gemologist appraiser, connecticut

 

 

 

 

Apatite

 

Color: blue, green, yellow, pink, violet, colorless.


Moh’s Hardness: 5


Refractive Index: 1.632-1.646


Critical Angle: 37.84°


Specific Gravity: 3.17-3.23


Cleavage: Poor, imperfect


Fracture: Conchoidal, brittle


Dispersion: Medium (.013-.016)


Heat Sensitivity: High


Dichroic: Strong to weak depending on the color


Birefringence (double refraction): Weak (.002-.004)


Crystal Structure: Hexagonal

 

Treatments: Blue/green, blue Apatite is usually heat treated to bring out the blue color and to remove silk.

 

 

 

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