metamorphic
Dark metamorphic rock, possibly amphibolite
Amphibolite (tentative; commonly hornblende and plagioclase)
AI-generated identification · may be incorrectDark gray-green, coarse to medium-grained, with a rough, mottled surface and weakly visible mineral alignment. Amphibole hardness is about 5–6 on the Mohs scale; the image does not allow reliable identification of luster, cleavage, or specific gravity.
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Physical properties
Dark gray-green, coarse to medium-grained, with a rough, mottled surface and weakly visible mineral alignment. Amphibole hardness is about 5–6 on the Mohs scale; the image does not allow reliable identification of luster, cleavage, or specific gravity.
Formation & geological history
Amphibolite forms when basaltic or gabbroic rocks are metamorphosed under moderate-to-high heat and pressure. Such rocks occur in many Precambrian and younger metamorphic belts; the specimen’s age cannot be determined from the photo.
Uses & applications
Amphibolite is used locally as crushed stone, aggregate, and dimension stone; attractive pieces may be collected or polished.
Geological facts
The pictured specimen is consistent with a dark, amphibole-rich rock, but other dark rocks—such as basalt or hornblende-rich gneiss—can look similar.
Field identification & locations
A firm identification requires examining fresh surfaces and mineral grains; amphibolite commonly contains visible dark hornblende and lighter plagioclase. Found in metamorphic terrains worldwide.
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