metamorphic
Weathered metamorphic rock, likely greenschist or amphibolite
Chlorite–actinolite schist/amphibolite; composition likely quartz, feldspar, chlorite, amphibole, and epidote
AI-generated identification · may be incorrectFine- to medium-grained, mottled gray-green and brown surface with weak foliation and rounded weathering; typical hardness about 5–6 Mohs, dull to subtly silky luster, and no obvious cleavage visible at this scale.
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Physical properties
Fine- to medium-grained, mottled gray-green and brown surface with weak foliation and rounded weathering; typical hardness about 5–6 Mohs, dull to subtly silky luster, and no obvious cleavage visible at this scale.
Formation & geological history
Formed when basaltic or mafic volcanic rock was altered by regional metamorphism, commonly during mountain building; its exact geological age cannot be determined from the photograph.
Uses & applications
Primarily a collectible or educational specimen; related durable metamorphic rocks may be used as crushed stone, riprap, or decorative aggregate, but this small piece has little commercial use.
Geological facts
The green coloration commonly reflects chlorite, actinolite, or epidote produced during low- to medium-grade metamorphism and hydrothermal alteration.
Field identification & locations
Look for planar mineral alignment, green amphibole/chlorite, a granular rather than glassy texture, and a lack of vesicles; common in metamorphic belts worldwide, including regions of the Appalachians, Alps, and Pacific Northwest.
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