metamorphic

Weathered greenstone pebble

Metamorphosed mafic rock, commonly metabasalt or greenschist (exact identification requires testing)

AI-generated identification · may be incorrect

Dense, fine-grained, rounded, dull green-gray surface with dark veins or fractures; typically Mohs 5–7, nonmetallic luster, and no visible cleavage. Green color commonly comes from chlorite, epidote, actinolite, or serpentine.

Identified August 13, 2026More metamorphic →

Explore Weathered greenstone pebble 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 formed when basaltic volcanic rock was altered by low- to medium-grade metamorphism, often during regional tectonic burial; age depends on its source terrain. Stream or soil transport rounded the specimen and weathering produced its muted surface.

Uses & applications

Common greenstone is used as aggregate, landscaping stone, and occasionally carved ornamental material; attractive pieces may be collected but are generally not gem-grade.

Geological facts

“Greenstone” is a field term covering several rocks, not one mineral. A fresh broken surface, streak, magnetism, acid reaction, and hardness testing are needed to distinguish metabasalt, serpentinite, epidote-rich rock, or other possibilities.

Field identification & locations

Common in regions with ancient volcanic and metamorphic belts, including the Appalachian, Pacific Northwest, and many ophiolite zones. Collector value is usually $1–$10 for a hand specimen, potentially $20–$50 if unusually attractive or compositionally distinctive.