metamorphic

Banded amphibolite

Amphibolite, chiefly hornblende and plagioclase, with light-colored quartz- or feldspar-rich bands

AI-generated identification · may be incorrect

Dark green-black, coarse crystalline rock with pale mineral bands or veins; amphibole has Mohs hardness about 5–6 and plagioclase 6–6.5. The specimen’s minerals and exact composition cannot be confirmed from the image alone.

Identified October 6, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when basaltic or gabbroic rocks undergo medium- to high-grade metamorphism; banding may reflect mineral segregation or later veins. Such rocks occur across many geological ages.

Uses & applications

Used as crushed stone, aggregate, and occasionally decorative building stone; banded pieces are mainly collected as specimens.

Geological facts

Amphibolite is named for its abundant amphibole minerals, commonly hornblende. Its dark-and-light banding can resemble gneiss, though amphibolite is typically richer in dark amphibole.

Field identification & locations

Look for dark, elongated amphibole crystals intergrown with lighter feldspar and a hard, crystalline texture; field identification is best confirmed by mineral testing. Amphibolite occurs in metamorphic belts worldwide.