metamorphic

Banded greenstone or altered basalt

Chlorite–epidote amphibolite/greenstone; exact identification requires testing

AI-generated identification · may be incorrect

Dark green-gray, fine-grained, opaque, with a contrasting white mineral vein or band likely quartz or calcite. Typical hardness is about 5–7 Mohs, dull to weakly waxy luster, massive texture, and no obvious cleavage; the rounded shape appears polished or naturally waterworn.

Identified September 6, 2026More metamorphic →

Explore Banded greenstone or altered basalt in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Likely metamorphosed mafic volcanic rock formed during low- to medium-grade regional metamorphism, with a later silica- or carbonate-rich fracture vein. Such rocks range from Precambrian to much younger geologic ages and commonly occur in greenstone belts or altered volcanic terrains.

Uses & applications

Used as decorative stone, cabochons, carvings, and lapidary material; comparable greenstones can also serve as aggregate or building stone. This small specimen has limited commercial value unless provenance or unusual mineralogy is established.

Geological facts

Green color commonly comes from chlorite, epidote, actinolite, or serpentine replacing pyroxene and feldspar. The white band should fizz in dilute hydrochloric acid if it is calcite, but not if it is quartz.

Field identification & locations

Look for a dense dark-green matrix, fine grain, and a sharply contrasting vein; a steel knife, glass plate, streak, magnet, acid, and hand lens can help distinguish components. Common sources include the Canadian Shield, New England, Scandinavia, Australia, and southern Africa.