igneous
Copper-bearing basalt or volcaniclastic rock
Cuprite–malachite-bearing mafic volcanic rock; likely basalt with copper sulfides/oxides
AI-generated identification · may be incorrectDark gray-black, very fine-grained and vesicular, with metallic patches and green-blue secondary copper minerals. Basaltic groundmass is typically Mohs 5–6, whereas malachite is 3.5–4 and copper sulfides are ~2.5–4; luster ranges dull to metallic.
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Physical properties
Dark gray-black, very fine-grained and vesicular, with metallic patches and green-blue secondary copper minerals. Basaltic groundmass is typically Mohs 5–6, whereas malachite is 3.5–4 and copper sulfides are ~2.5–4; luster ranges dull to metallic.
Formation & geological history
Likely formed from mafic lava or volcanic breccia, later altered by oxygenated groundwater that converted copper sulfides to malachite, azurite, and possibly cuprite. The precise age and locality cannot be determined from the image.
Uses & applications
Primarily a mineral-collecting specimen; copper-rich material may have limited ore value, but this rough piece is unsuitable for construction or jewelry without cutting and stabilization.
Geological facts
The vivid green-blue spots are characteristic of oxidized copper minerals, commonly malachite and azurite, rather than the host rock itself.
Field identification & locations
Look for a dark basaltic matrix, vesicles, metallic copper minerals, and green-blue coatings; a streak, hardness, acid, and conductivity test would help confirm identification. Common settings include porphyry-copper and volcanic hydrothermal districts.
