metamorphic
Amphibolite (likely)
Amphibolite, chiefly hornblende and plagioclase feldspar
AI-generated identification · may be incorrectDark gray, coarse-grained, with pale mineral streaks and a mottled, weakly foliated texture; typically Mohs 5–6, vitreous to dull, with interlocking crystals and no prominent cleavage. Exact identification requires examination of the minerals; the photograph alone is not definitive.
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Physical properties
Dark gray, coarse-grained, with pale mineral streaks and a mottled, weakly foliated texture; typically Mohs 5–6, vitreous to dull, with interlocking crystals and no prominent cleavage. Exact identification requires examination of the minerals; the photograph alone is not definitive.
Formation & geological history
Forms when basaltic or gabbroic rocks undergo medium- to high-grade metamorphism, commonly during mountain building; its age depends on the source rock and metamorphic event.
Uses & applications
Used as crushed stone and sometimes as dimension stone or decorative landscaping rock; ordinary specimens have little jewelry value.
Geological facts
Amphibolite’s dark amphibole minerals and lighter feldspar make a characteristic salt-and-pepper appearance.
Field identification & locations
Look for coarse, interlocking dark amphibole and pale feldspar, often with aligned crystals; it occurs in metamorphic belts worldwide. A photo cannot confirm the mineral composition.
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