metamorphic
Likely chlorite schist or altered mafic rock
Chlorite–actinolite schist; commonly composed of chlorite, actinolite/amphibole, epidote, and albite
AI-generated identification · may be incorrectDark green to black, dull to slightly silky, fine- to medium-grained, with a weakly foliated texture; approximate Mohs hardness 2–6 and specific gravity about 2.8–3.3. The photograph lacks enough detail for confident mineral identification.
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Physical properties
Dark green to black, dull to slightly silky, fine- to medium-grained, with a weakly foliated texture; approximate Mohs hardness 2–6 and specific gravity about 2.8–3.3. The photograph lacks enough detail for confident mineral identification.
Formation & geological history
Forms when basaltic or other iron- and magnesium-rich rocks undergo low- to medium-grade metamorphism, commonly in oceanic crust or subduction-related settings. Ages vary widely from Precambrian to recent tectonic belts.
Uses & applications
Usually a collector specimen; tougher schist varieties may be used locally as decorative or dimension stone, but this irregular piece has little industrial or jewelry use.
Geological facts
Green coloration commonly reflects chlorite, actinolite, or epidote produced during hydrothermal alteration and metamorphism. Some specimens can be weakly magnetic if magnetite is present.
Field identification & locations
Look for green-black color, foliation, sparkly cleavage surfaces, and associated white feldspar or epidote; a streak, hardness, magnetism, and thin-section test would improve identification. Common in metamorphic belts worldwide, including the Alps, Appalachians, New Zealand, and Japan.
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