metamorphic
Polished greenstone pebble
Likely chlorite- or actinolite-bearing greenstone (metamorphosed mafic rock)
AI-generated identification · may be incorrectDark olive-green, fine-grained, mottled and polished; typically Mohs 5–6, with a dull to weakly vitreous luster and no obvious cleavage. Exact mineral composition cannot be confirmed from the photograph.
Identified More metamorphic →
Explore Polished greenstone pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark olive-green, fine-grained, mottled and polished; typically Mohs 5–6, with a dull to weakly vitreous luster and no obvious cleavage. Exact mineral composition cannot be confirmed from the photograph.
Formation & geological history
Greenstone forms when basalt or related mafic rock is altered by low-grade metamorphism and hydrothermal fluids; its age depends on the source rock and cannot be determined visually.
Uses & applications
Used as a decorative pebble, carving material, and occasionally for beads or small ornaments; greenstone varieties have also been used historically for tools.
Geological facts
The term “greenstone” describes color and alteration, not one unique mineral or precise rock composition.
Field identification & locations
Look for a dense, fine-grained green rock with darker mineral flecks; common in ancient volcanic belts and glacial or stream deposits. The pictured stone appears tumbled or naturally rounded.
More like this
Other metamorphic specimens
Nephrite Jade
Nephrite
Mineral/Rock
Amphibolite
Amphibolite
metamorphic
Rhodonite
Manganese Silicate (Mn, Fe, Mg, Ca)SiO3
mineral
Rhodonite
(Mn,Fe,Mg,Ca)SiO3
mineral
Greenschist
Greenschist (containing Chlorite, Actinolite, and Epidote)
metamorphic
Garnet
Garnet group: X3Y2(SiO4)3 (commonly Almandine-Pyrope series)
mineral