mineral
Blue-green copper mineral-bearing rock, likely chrysocolla with malachite
Chrysocolla (hydrated copper aluminosilicate, approximately (Cu,Al)₂H₂Si₂O₅(OH)₄·nH₂O) with malachite (Cu₂CO₃(OH)₂), possibly in altered host rock
AI-generated identification · may be incorrectTypically turquoise-blue to green, opaque, earthy to waxy or vitreous luster, amorphous or cryptocrystalline, and Mohs hardness about 2.5–4; malachite commonly forms green bands or patches. The specimens appear rough and massive, with no obvious cleavage.
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Physical properties
Typically turquoise-blue to green, opaque, earthy to waxy or vitreous luster, amorphous or cryptocrystalline, and Mohs hardness about 2.5–4; malachite commonly forms green bands or patches. The specimens appear rough and massive, with no obvious cleavage.
Formation & geological history
Forms in oxidized zones above copper deposits when copper-rich fluids alter silica- and aluminum-bearing rock; commonly associated with quartz, limonite, azurite, and native copper. Formation is generally geologically young relative to the host deposit, occurring during near-surface weathering.
Uses & applications
Used as a decorative stone, cabochon material, pigment historically, and copper ore when abundant; attractive polished material has modest lapidary value.
Geological facts
Chrysocolla’s intense blue-green color comes from hydrated copper; it is often sold commercially as “chrysocolla-malachite” or “gem silica” when silica-rich and durable.
Field identification & locations
Look for blue-green color, irregular mottling, association with brown iron oxides, and a soft scratch response; avoid acids and prolonged soaking. Common localities include Arizona, Nevada, Chile, Peru, the Democratic Republic of Congo, and Russia.
