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Dioptase

dioptase
Emerald green dioptase

Dioptase is a beautiful, vivid emerald-green, having a hint of blue. It has very high fire, but this is masked by its strong color, which may make stones translucent rather than transparent. Prized by the collector for its colour, it is nonetheless rarely faceted, as stones are brittle and fragile, and too soft to be worn. It is sometime wrongly identified as emerald.

The best quality dioptase is found in copper deposits in Russia, Namibia, Zaire, Chile, and Arizona (USA).

Dioptase Pictures

Rough dioptase

Cause of Color : Broad band centered at 550nm and strong absorption in the blue and violet region.
Chemical Composition :

Copper Silicate – CuSiO2(OH)2


Crystal System / Forms :

Trigonal System / Prismatic crystals.


Cuts & Uses :

Facetted, cabochon cut, sometimes as beads for jewelry making.


Dispersion : 0.036
Hardness : 5
Lustre : Vitreous
Magnification :

3 directional cleavage cracks, doubling.


Optic Character :

Anisotropic, D.R.; Uniaxial positive.


Pleochroism : Weak
Refractive Index / Birefringence :

1.644 – 1.697 / 0.053; Range: 1.633 – 1.710


Simulants (with separation tests) :
  • Natural / synthetic emerald (R.I., birefringence, S.G.), Peridot (inclusions, spectrum), Diopside (R.I., birefringence)

Sources :

Russia, Zaire, Chile, Namibia, U.S.A.


Specific Tests :
  • Very intense green
  • Strong doubling
  • Attacked by acids

Spectrum :

Copper


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