metamorphic

Greenstone / altered basalt (probable)

Chlorite–actinolite–epidote rock; commonly derived from basalt or gabbro

AI-generated identification · may be incorrect

Fine-grained, gray-green, dull to weakly waxy luster with irregular fractures and faint foliation; typical hardness about 5–6 Mohs, though exact properties vary with mineral composition. The rounded shape appears naturally weathered or manually smoothed.

Identified September 13, 2026More metamorphic →

Explore Greenstone / altered basalt (probable) 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 by low- to moderate-grade metamorphism or hydrothermal alteration of mafic volcanic rock, commonly during ancient oceanic crust formation; precise age cannot be determined visually. Common in greenstone belts, altered basalt terrains, and subduction-related rocks.

Uses & applications

Used locally as durable aggregate, landscaping stone, carving material, or a lapidary curiosity; this specimen does not appear gem quality. Greenstone artifacts and ornamental pieces can have cultural significance.

Geological facts

“Greenstone” is a field term rather than one exact mineral, and its color commonly comes from chlorite, actinolite, epidote, or serpentine.

Field identification & locations

Look for a dense green-gray body, fine grain, dark mafic streaks, and possible foliation; a knife-scratch test and streak, acid, or microscope examination would improve identification. Common worldwide, including greenstone belts in Australia, Canada, South Africa, and the United States.