metamorphic
Likely fine-grained greenstone
Greenstone, typically metamorphosed mafic volcanic rock (metabasalt; commonly chlorite- and actinolite-bearing)
AI-generated identification · may be incorrectFine-grained, gray-green and matte, with a dense, compact texture. Typical constituent minerals include chlorite, actinolite, epidote, and albite; hardness varies with composition, often around 5–6 Mohs. Exact identification requires closer examination.
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Physical properties
Fine-grained, gray-green and matte, with a dense, compact texture. Typical constituent minerals include chlorite, actinolite, epidote, and albite; hardness varies with composition, often around 5–6 Mohs. Exact identification requires closer examination.
Formation & geological history
Forms when basalt or other mafic volcanic rock is altered by low-grade metamorphism and hydrothermal fluids. Such rocks occur in ancient and modern metamorphic terranes; this specimen’s age and origin cannot be determined from the image.
Uses & applications
Used as decorative or landscaping stone and, when suitable, for carving or polished objects; specimens are also collected.
Geological facts
“Greenstone” describes a rock’s color and alteration, not one uniquely defined mineral or composition.
Field identification & locations
Look for a dense, fine-grained greenish-gray surface, sometimes with subtle chlorite or epidote flecks. Common in metamorphosed volcanic belts; the pictured piece may also be another fine-grained stone, so field or laboratory tests are needed for confirmation.
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