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Dioptase

Unknown17.24 |
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 Properties

Chemical Composition: 
Copper Silicate - CuSiO2(OH)2
Colors / Varieties: 
Emerald green, bluish green (over saturated color)
Crystal System / Forms: 
Trigonal System / Prismatic crystals.
Hardness: 
5
Specific Gravity: 
3.28 - 3.35
Cleavage / Fracture: 
Perfect 3 directional cleavage / Conchoidal fracture
Optic Character: 
Anisotropic, D.R.; Uniaxial positive.
Lustre: 
Vitreous
Refractive Index / Birefringence: 
1.644 - 1.697 / 0.053; Range: 1.633 - 1.710
Pleochroism: 
Weak
Dispersion: 
0.036
Magnification: 
3 directional cleavage cracks, doubling.
U.V. Fluorescence: 
Inert.
Spectrum: 
Copper
Cause of Color: 
Broad band centered at 550nm and strong absorption in the blue and violet region.
Specific Tests: 
  • Very intense green
  • Strong doubling
  • Attacked by acids
Simulants (with separation tests): 
  • Natural / synthetic emerald (R.I., birefringence, S.G.), Peridot (inclusions, spectrum), Diopside (R.I., birefringence)
Geological Occurrence: 
In the oxidized zones of copper deposits. Clean specimens are generally in sizes below 1.5 carat.
Sources: 
Russia, Zaire, Chile, Namibia, U.S.A.
Cuts & Uses: 
Facetted, cabochon cut, sometimes as beads for jewelry making.