metamorphic
Likely amphibolite
Amphibolite, composed chiefly of hornblende and plagioclase
AI-generated identification · may be incorrectDark gray-green, coarse crystalline rock with a glittering luster; likely hardness about 5–6, with interlocking crystals and no prominent cleavage at hand-specimen scale. Exact mineral composition cannot be confirmed from the photo.
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Physical properties
Dark gray-green, coarse crystalline rock with a glittering luster; likely hardness about 5–6, with interlocking crystals and no prominent cleavage at hand-specimen scale. Exact mineral composition cannot be confirmed from the photo.
Formation & geological history
Typically forms when basaltic or gabbroic rocks undergo medium- to high-grade metamorphism; its age depends on the local geology and cannot be determined visually.
Uses & applications
Used as crushed stone and, when attractive and sound, as dimension stone or a collector specimen.
Geological facts
The pale reflective grains may be amphibole or feldspar, but a photograph alone is insufficient to identify the minerals confidently.
Field identification & locations
Look for a dense, dark green-to-black rock with visible interlocking amphibole and feldspar crystals; amphibolite occurs in metamorphic belts worldwide. A streak, hardness, and mineral tests would help distinguish it from other dark crystalline rocks.
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