metamorphic

Tumbled greenstone pebble

Greenstone (metamorphosed mafic volcanic rock; commonly chlorite, actinolite, epidote, and albite)

AI-generated identification · may be incorrect

Small, rounded, polished, mottled dark green-gray pebble with a subdued luster. Hardness varies roughly 5–7 Mohs; typically fine-grained, with no visible cleavage or distinct crystals.

Identified October 5, 2026More metamorphic →

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Physical properties

Small, rounded, polished, mottled dark green-gray pebble with a subdued luster. Hardness varies roughly 5–7 Mohs; typically fine-grained, with no visible cleavage or distinct crystals.

Formation & geological history

Likely basalt or similar mafic lava altered by low-grade metamorphism and later rounded by water or tumbling. Greenstone forms in ancient oceanic crust and other metamorphic settings; age depends on source.

Uses & applications

Commonly sold as a tumbled stone or used in crafts, beads, and decorative objects; greenstone also has historical use as a toolstone.

Geological facts

“Greenstone” is a broad descriptive name, not a single mineral species; its green color usually comes from alteration minerals such as chlorite or actinolite.

Field identification & locations

Identify by its dense, fine-grained texture and green color; a scratch test and examination of a fresh surface help distinguish it from softer green minerals. Found in metamorphosed volcanic belts worldwide.