mineral
Tumbled malachite (probable)
Malachite, Cu₂CO₃(OH)₂
AI-generated identification · may be incorrectPolished/tumbled opaque vivid green stone with darker green banding and botryoidal-looking patterns; vitreous to silky luster. Mohs hardness 3.5–4, monoclinic crystal system, perfect cleavage in one direction, specific gravity about 3.6–4.0.
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Physical properties
Polished/tumbled opaque vivid green stone with darker green banding and botryoidal-looking patterns; vitreous to silky luster. Mohs hardness 3.5–4, monoclinic crystal system, perfect cleavage in one direction, specific gravity about 3.6–4.0.
Formation & geological history
A secondary copper-carbonate mineral formed near the surface in oxidized zones of copper deposits, commonly replacing copper sulfides. It is geologically young relative to its host rocks and occurs in many ore systems.
Uses & applications
Used as an ornamental and lapidary material, pigment, cabochons, beads, and collector specimens; too soft for durable everyday rings. Avoid dust or ingestion because copper minerals can be harmful if powdered.
Geological facts
The image strongly supports malachite, though chrysocolla or dyed green stone are possible without testing. Its characteristic concentric or irregular dark/light green banding is the key visual clue.
Field identification & locations
Common sources include the Democratic Republic of Congo, Zambia, Russia, Australia, and Arizona; it is not especially diagnostic of the Portland-area geology. Confirm with hardness (it scratches with a steel knife) and a streak test on an inconspicuous area; malachite gives a pale green streak.
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