metamorphic
Greenschist
Greenschist facies metamorphic rock; commonly chlorite–actinolite–epidote schist
AI-generated identification · may be incorrectTypically fine- to medium-grained, green to gray-green, with a silky to dull luster and weak foliation; hardness is approximately 5–6, depending on mineral content. The specimen appears rounded and weathered, likely a small metamorphic pebble.
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Physical properties
Typically fine- to medium-grained, green to gray-green, with a silky to dull luster and weak foliation; hardness is approximately 5–6, depending on mineral content. The specimen appears rounded and weathered, likely a small metamorphic pebble.
Formation & geological history
Formed when basaltic or mafic volcanic rock undergoes low- to medium-grade metamorphism, commonly during mountain building; many examples are Paleozoic to Precambrian. Typical minerals include chlorite, actinolite, epidote, albite, quartz, and minor biotite.
Uses & applications
Used locally as decorative stone, aggregate, and teaching or collecting material; attractive foliated pieces may be polished, though it is not usually a gemstone.
Geological facts
Its green color reflects abundant chlorite, actinolite, or epidote. Greenschist records metamorphic conditions of roughly 300–500 °C and moderate pressure.
Field identification & locations
Identify it by its green color, fine foliation, elongated mineral streaks, and lack of obvious glassy volcanic texture; a hand lens or thin section is useful for confirmation. Common in metamorphic belts worldwide, including Appalachians, Alps, and New Zealand.
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