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Dioptase is a brightly colored mineral, highly desired for its intense green color. It can form in very distinctive, well-developed crystals, but only a handful of well-known deposits have produced large crystals. Most localities of this mineral, including those in Arizona, only produce microcrystals. Dioptase crystals are generally fragile and can easily break or crumble, and therefore care must be exercised when handling specimens. Dioptase was named in 1797. Its name is derived from a combination of the Greek words Dia, which means "through" and Optasia, which means "to see". This is regarding the ability to see internal cleavage planes within transparent to translucent crystals of Dioptase. |
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Chemical Formula |
Cu6Si6O18 ·6H2O |
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Composition |
Hydrous copper silicate |
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Color |
Deep emerald green, dark green, bluish-green |
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Streak |
Green |
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Hardness |
5 |
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Crystal System |
Hexagonal |
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Crystal Forms
and Aggregates |
In distinct, hexagonally-shaped crystals with pointed, rhombohedral ends. Crystals are almost almost always doubly terminated, and are usually short and stubby, although they are occasionally prismatic and elongated. Crystals may also be more typical rhombohedral, though this habit is very uncommon. Crystals are usually in dense groups of interconnected crystals, but may be as isolated individuals. Also drusy, radiating, acicular, botryoidal, grainy, encrusting, and massive.
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Transparency |
Transparent to nearly opaque |
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Specific Gravity |
3.3 - 3.4 |
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Luster |
Vitreous to adamantine |
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Cleavage |
1,3 |
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Fracture |
Uneven |
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Tenacity |
Brittle |
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In Group |
Silicates; Cyclosilicates |
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Striking Features |
Distinctive color and crystal habits |
| Environment |
As a secondary mineral in hydrothermal replacement copper deposits.
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| Rock Type |
Sedimentary, Metamorphic |
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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3 |
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Demand (1-3) |
1 |
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Dioptase is a highly valued mineral, and good crystals are sought out by mineral collectors and enthusiasts. Dioptase specimens, especially those from classic localities, can be quite costly.
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The type locality for Dioptase, known for producing large and exceptional crystals, is Altyn-Tyube, Kazakhstan. Equally exceptional is the famous locality of Tsumeb, Namibia, which has produced what are perhaps the best examples of this mineral. The copper mines of the Kaokoveld District, Kunene Region, Namibia have produced large, isolated and outstanding Dioptase crystals associated with bright blue Shattuckite in very aesthetic combinations. Other important African localities are the Katanga (Shaba) Copper Belt, in the Congo (Zaire); and Mindouli and Renéville, in the Republic of Congo. In South America, good Dioptase crystals come from the Malpaso Quarry, Dumesnil, Córdoba, Argentina.
In the U.S., Dioptase is mostly limited to the state of Arizona, and only in small drusy or encrusting crystals, as well as radiating microcrystals. Important Arizona localities include the Mammoth-St. Anthony Mine, Tiger, Pinal Co.; the Christmas Mine near Hayden, Gila Co.; and the Morenci Mine, Greenlee Co.
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Uvarovite - Different crystal forms and environment and harder.
Malachite and Brochantite - Different crystal forms, lower hardness.
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Have a question about Dioptase? Visit our Q&A Community and ask the experts!
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