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.
| Data | Value |
|---|---|
| Name | Dioptase |
| Colors | Rich emerald green, bluish green. |
| Crystallography | Hexagonal. Fine crystals are common in certain localities; stubby, elongated. |
| Refractive Index | 1.644-1.709 |
| Luster | Vitreous. |
| Fracture Luster | Greasy. |
| Hardness | 5 |
| Fracture | Conchoidal to uneven |
| Specific Gravity | 3.28-3.35 |
| Birefringence | 0.053 |
| Cleavage | Perfect 1 direction |
| 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 |
| Luminescence Present | No |
| Transparency | Translucent to transparent. |
| Absorption Spectrum | Broad band at about 5500; strong absorption of blue and violet. |
| Formula |
CuSiO2(OH)2. |
| Optics |
o = 1.644-1.658; e = 1.697-1.709. Uniaxial (+). |
| Optic Sign | Uniaxial + |
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.
Streak testing is a destructive gemstone test rarely used by gemologists. Most gems leave no streak. Learn which gems do and what color they…
Some gems are seldom faceted because they’re rarely found in nature or rarely used for jewelry. Learn a few tricks for faceting seven exotic gemstones.…
IGS Newsletter
