metamorphic

Greenstone (likely altered basalt)

Metabasalt, commonly composed of actinolite, chlorite, epidote, albite, and quartz

AI-generated identification · may be incorrect

Fine-grained, dull to faintly silky luster, gray-green color with rusty weathering; typically Mohs 5–6, tough, with no obvious cleavage and a compact crystalline texture. Exact identification requires thin-section or chemical testing.

Identified September 16, 2026More metamorphic →

Explore Greenstone (likely 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

Formed when basaltic lava was metamorphosed under low- to medium-grade greenschist-facies conditions, commonly during ancient ocean-floor or mountain-belt processes. The specimen’s geological age cannot be determined from the image.

Uses & applications

Used locally as durable aggregate, road stone, landscaping material, and occasionally carved into tools or ornaments; attractive pieces are collected as greenstone.

Geological facts

The term “greenstone” is descriptive rather than a single mineral name and may also refer to altered rocks such as serpentinite or green schist.

Field identification & locations

Look for a dense, fine-grained green-gray body, high toughness, and possible epidote or chlorite speckling; a streak, hardness, acid, and magnetic test can help distinguish it from serpentinite or ordinary basalt. Common in ancient volcanic and metamorphic belts worldwide.