metamorphic
Weathered mafic metamorphic rock, likely amphibolite
Amphibolite; chiefly hornblende amphibole and plagioclase feldspar, with minor biotite, quartz, or garnet
AI-generated identification · may be incorrectDark green-black, coarse-grained, mottled, and commonly weakly foliated; vitreous to dull luster, Mohs hardness about 5–6, specific gravity roughly 2.9–3.2. The image suggests rounded weathering and iron staining, though exact identification requires a fresh surface or testing.
Identified More metamorphic →
Explore Weathered mafic metamorphic rock, likely amphibolite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark green-black, coarse-grained, mottled, and commonly weakly foliated; vitreous to dull luster, Mohs hardness about 5–6, specific gravity roughly 2.9–3.2. The image suggests rounded weathering and iron staining, though exact identification requires a fresh surface or testing.
Formation & geological history
Forms when basaltic or gabbroic protoliths undergo medium- to high-grade regional metamorphism, typically during mountain building. Its age varies widely from Precambrian to modern tectonic belts.
Uses & applications
Used locally as crushed aggregate, road stone, dimension stone, and occasionally architectural facing; attractive polished pieces are mainly collector specimens rather than jewelry material.
Geological facts
Amphibolite commonly preserves evidence of ancient oceanic crust or mafic magma transformed by pressure and heat. Hornblende crystals may show elongated or splintery forms on a broken surface.
Field identification & locations
Look for a dense dark-green rock with interlocking amphibole and pale feldspar; it is harder and less vesicular than basalt. Common in metamorphic belts worldwide, including Scandinavia, Canada, the northeastern United States, and the Alps.
More like this
