metamorphic

Dark foliated metamorphic rock, likely amphibolite

Amphibolite, typically composed mainly of hornblende and plagioclase feldspar

AI-generated identification · may be incorrect

Dark gray-green, coarse to medium-grained with visible light-colored mineral patches and weak foliation. Typical hardness is about 5–6 on Mohs; luster is mostly dull to slightly vitreous, with no consistent cleavage at hand-specimen scale.

Identified September 26, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when basaltic or gabbroic rock is metamorphosed under moderate-to-high temperatures and pressure, commonly during mountain building. Its age cannot be determined from the photograph.

Uses & applications

Used as crushed aggregate, road stone, and dimension stone; attractive pieces may be kept as specimens or polished decoratively.

Geological facts

Amphibolite is named for its abundant amphibole minerals, especially hornblende; its composition and texture can vary considerably.

Field identification & locations

The dark, dense appearance and pale feldspar patches are consistent with amphibolite, but the image alone cannot confirm the identification. Common in metamorphic belts worldwide; check for interlocking hornblende crystals and banding.