metamorphic
Amphibolite pebble
Amphibolite, chiefly hornblende and plagioclase feldspar
AI-generated identification · may be incorrectDark gray-green, coarse to medium-grained, with a speckled appearance and no obvious cleavage on the rounded surface. Typical hardness is about 5–6 on the Mohs scale; luster is mostly dull to slightly vitreous, and the rock is commonly dense.
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Physical properties
Dark gray-green, coarse to medium-grained, with a speckled appearance and no obvious cleavage on the rounded surface. Typical hardness is about 5–6 on the Mohs scale; luster is mostly dull to slightly vitreous, and the rock is commonly dense.
Formation & geological history
Forms when mafic igneous rocks such as basalt or gabbro undergo medium- to high-grade metamorphism. Its exact age cannot be determined from the image; amphibolites occur in ancient metamorphic belts worldwide.
Uses & applications
Used as crushed aggregate, road stone, and dimension stone; attractive pieces may be collected or polished.
Geological facts
The visible dark minerals are likely amphibole, while lighter grains may be plagioclase; a photograph cannot confirm the identification or mineral proportions.
Field identification & locations
Look for a dark, heavy rock with interlocking dark amphibole and pale feldspar grains; rounded shape suggests transport by water or glacial action. Common in metamorphic terrains and river or beach gravels.
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