metamorphic

Likely amphibolite

Amphibolite, composed mainly of hornblende (amphibole) and plagioclase feldspar

AI-generated identification · may be incorrect

Dark gray-green, coarse to medium-grained, with a subtle foliated or streaky texture and dull to slightly vitreous luster. Typical hardness is about 5–6 on Mohs; exact mineral proportions cannot be confirmed from the photo.

Identified October 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when basaltic or gabbroic rock undergoes medium- to high-grade metamorphism. Such rocks occur in ancient metamorphic belts, commonly formed hundreds of millions to billions of years ago.

Uses & applications

Used as crushed stone and aggregate; attractive, sound pieces may be cut or polished for decorative stone and collected as hand specimens.

Geological facts

Amphibolite’s dark color comes largely from iron- and magnesium-rich amphibole minerals. The specimen’s identification is provisional from appearance alone.

Field identification & locations

Look for dark hornblende-rich grains, pale feldspar flecks, and weak alignment of minerals; confirm with a fresh surface or mineral tests. Amphibolite occurs in metamorphic terrains worldwide.