metamorphic

Likely amphibolite (dark hornblende-rich rock)

Amphibolite, typically composed mainly of hornblende and plagioclase feldspar

AI-generated identification · may be incorrect

Dark gray to black, rough and crystalline with possible lighter feldspar streaks; hornblende has Mohs hardness about 5–6, while plagioclase is about 6. The small, weathered specimen does not reveal crystal structure or cleavage clearly.

Identified September 25, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when basalt or gabbro is metamorphosed under medium- to high-grade heat and pressure, commonly during mountain building. Its exact age cannot be determined from the image.

Uses & applications

Used as crushed stone, aggregate, and occasionally dimension stone; attractive pieces may be kept as geological specimens.

Geological facts

Amphibolite is named for amphibole minerals, especially hornblende, and commonly develops a coarse, interlocking texture.

Field identification & locations

Look for a dense, dark, crystalline rock with visible elongated amphibole grains and occasional pale feldspar. It occurs in metamorphic belts worldwide; a photograph alone cannot confirm this identification.