Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Dioptase is abundant in mineral collections throughout the world and is not considered a great rarity, but faceted gems are extremely rare due to a paucity of clean fragments. Clean stones over 1 carat are virtually nonexistent, and few collections have stones at all. Cabochons are blue-green, translucent, and quite attractive but are much too soft for wear.
Dioptase Value
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Dioptase Information
| Data | Value |
| Name | Dioptase |
| Crystallography | Hexagonal. Fine crystals are common in certain localities; stubby, elongated. |
| Colors | Rich emerald green, bluish green. |
| Luster | Vitreous; greasy on fractures. |
| Hardness | 5 |
| Density | 3.28-3.35 |
| Birefringence | 0.053 |
| Cleavage | Perfect I direction. Fracture conchoidal to uneven. Brittle. |
| Dispersion | 0.036 |
| Stone Sizes | Crystals may be fairly large, but clean areas within such crystals are always very small, and stones are never larger than 1-2 carats. Cabochons up to about 15 carats are sometimes cut from translucent masses. |
| Luminescence | None |
| Spectral | Broad band at about 5500; strong absorption of blue and violet. |
| Formula | CuSiO2(OH)2. |
Dioptase Information
Streak: Pale blue-green.
Optics: o = 1.644-1.658; e= 1.697-1.709. Uniaxial (+).
Occurrence: Oxidized zone of copper deposits. Zaire; Chile; USSR
Arizona: microscopic crystals.
Guchab and Tsumeb, Namibia: world’s finest crystals, some transparent but mostly filled with cleavage planes and fractures. These crystals are a superb color, on matrix, and up to 2 inches long.
Comments: Dioptase is abundant in mineral collections throughout the world and is not considered a great rarity, but faceted gems are extremely rare due to a paucity of clean fragments. Clean stones over 1 carat are virtually nonexistent, and few collections have stones at all. Cabochons are blue-green, translucent, and quite attractive but are much too soft for wear.
Name: From Greek words meaning to see through because the cleavage directions can be determined just by looking into the crystals.
