Chrysocolla
Hydrated copper aluminum silicate, approx. (Cu,Al)2H2Si2O5(OH)4·nH2O
A vivid blue-green hydrated copper silicate, soft on its own but prized as a gem when hardened by intergrown quartz or chalcedony.
- Mohs hardness
- 2-4 (up to 7 when silicified)
- Color
- Blue to blue-green and cyan
- Type
- mineral
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Overview
Chrysocolla is a hydrated copper silicate that forms striking blue to blue-green crusts, botryoidal masses and seams in copper deposits. Its intense cyan color comes from copper, the same element behind turquoise and malachite.
In its pure form chrysocolla is quite soft and porous, but it is frequently intergrown with quartz or chalcedony, which raises its hardness and makes it usable as a gemstone. The hardest, most translucent gem material, chrysocolla chalcedony, is sold as "gem silica" and is highly valued.
Chrysocolla often occurs alongside malachite, azurite and turquoise, and these can be mixed in colorful patterned stones.
Formation & geology
Chrysocolla is a secondary mineral that forms in the oxidized weathering zones of copper ore bodies. As copper-bearing sulfides break down near the surface and react with silica-rich groundwater, chrysocolla precipitates as crusts, coatings and fillings.
It commonly occurs with other secondary copper minerals such as malachite, azurite, cuprite and native copper. When silica continues to deposit, chrysocolla can be replaced or impregnated by chalcedony to form durable gem silica.
Major sources include the copper mining districts of Arizona and Utah in the United States, plus Peru, Chile, the Democratic Republic of Congo, Mexico and Israel.
How to identify it
Look for vivid sky-blue to blue-green color in botryoidal crusts, veins or massive form, usually associated with copper minerals. Pure chrysocolla is soft (2-4), with a dull to waxy or earthy luster, and may stick slightly to the tongue due to its porosity.
Silicified gem material is much harder (up to 7), more translucent and glassy. Streak is white to pale blue-green.
Look-alikes include turquoise, variscite and dyed howlite. Turquoise is harder and usually more uniform; chrysocolla is often more vibrant cyan and softer, and may show intergrown black or green copper minerals. The soft, porous texture distinguishes raw chrysocolla from quartz-hardened gem silica.
Uses & significance
Hardened chrysocolla, especially gem silica chalcedony, is cut into cabochons, beads and inlay for jewelry, valued for its intense blue-green color. Softer material is stabilized or backed for use in cabochons.
It has historically been used as a copper ore indicator and as a pigment. The patterned mixtures with malachite and azurite (sometimes sold as Eilat stone) are popular in decorative lapidary work.
Metaphysically, chrysocolla is associated with communication, calm and the throat, though these claims are not scientific.
Frequently asked questions
Is chrysocolla a real gemstone if it is so soft?
Pure chrysocolla is soft, but it is usually intergrown with quartz or chalcedony, which hardens it enough to cut. The hardest form, gem silica, is highly prized.
What is gem silica?
Gem silica is translucent chrysocolla chalcedony, copper-colored chalcedony with a vivid blue-green hue and quartz hardness, the most valuable form of chrysocolla.
How is chrysocolla different from turquoise?
Both are blue-green copper minerals, but chrysocolla is generally softer, more porous and often more intensely cyan, while turquoise is harder and more uniform.
Why is chrysocolla blue-green?
Copper in its chemistry produces the blue to blue-green color, the same element responsible for malachite and azurite.
Where is chrysocolla found?
In oxidized copper deposits, notably in Arizona and Utah, as well as Peru, Chile, Mexico, Israel and the Congo.
Chrysocolla guides
In-depth guides for identifying, valuing, and understanding Chrysocolla.
Chrysocolla identified by the community
Real specimens identified with Rock Identifier.
