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Dioptase
Current inventory:  1 gem
 

Chemistry:  CuSiO₂(OH)₂

Discovered in 1797;   IMA status: Valid (pre-IMA; Grandfathered).
Dioptase was named in 1797 by Hauy from the Greek words dia for through and optomai for to see or vision in allusion to the visibility of internal cleavage planes.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/E.21-10

8 : Silicates
E : Cyclosilicates, triplet rings [Si3O9]6-
21 : Dioptase - Chrysocolla series

Crystal Data

Crystallography:

Trigonal - Rhombohedral

Crystal Habit:

Commonly in prismatic to rhombohedral crystals, to 5 cm. As indistinct crystalline aggregates and massive.

Twinning:

None

Physical Properties

Cleavage:

[1011] Perfect

Fracture:

Conchoidal to Uneven

Tenacity:

Brittle

Moh's Hardness:

5.0

Density:

3.28 - 3.35 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Pyroelectic

Optical Properties

Color:

Dark blue green, Emerald green, Turquoise

Transparency:

Transparent to Translucent

Luster:

Vitreous (glassy)

Refractive Index:

1.644 - 1.709  Uniaxial ( + )

Birefringence:

0.0510 - 0.0530

Dispersion:

0.036

Pleochroism:

Weak

Occurances

Geological Setting:

In the oxidized zone of some copper deposits.

Type Locality:

Altyn-Tyube (Altyn-Tube) deposit, Kirghiz Steppes (Asiatic Steppes), Qaraghandy Oblysy (Karaganda Oblast'), Kazakhstan

Year Discovered:

1797

View mineral photos:

Dioptase Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Dioptase is a popular mineral specimen for collectors but very rarely available as faceted gems due to lack of clean crystals and difficulty in faceting because of its perfect cleavage. Large, beautiful crystals are available from Tsumeb, Namibia but these are mostly filled with cleavage plans and fractures. Very small crystals are also found at a few US locations such as at the Mammoth-St. Anthony mine, Tiger, at Ray, and in the Table Mountain mine, Galiuro Mountains, Pinal County, Arizona; and in California, from the Blue Bell claims, near Baker, San Bernardino County.
 

  
Dioptase gems for sale: