igneous
Fine-grained green-gray rock pebble, likely basalt or greenstone
Probable basalt (plagioclase and pyroxene), possibly altered to greenstone
AI-generated identification · may be incorrectFine-grained, compact, dull to slightly granular surface; gray-green with pale mineral flecks. Typical basalt hardness is about 6; individual crystals are too small to identify, and the image alone cannot establish composition or specific gravity.
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Physical properties
Fine-grained, compact, dull to slightly granular surface; gray-green with pale mineral flecks. Typical basalt hardness is about 6; individual crystals are too small to identify, and the image alone cannot establish composition or specific gravity.
Formation & geological history
If basalt, formed when mafic lava cooled rapidly at or near Earth’s surface; greenstone can result from later low-grade metamorphic alteration. No geological age can be determined from the image.
Uses & applications
Commonly used as aggregate, road stone, and building stone; small pebbles may be kept as curiosities or used in crafts.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and commonly contains plagioclase and pyroxene.
Field identification & locations
A dark, fine-grained texture and pale flecks are consistent with basalt, but the rounded shape indicates abrasion and is not diagnostic. Basalt and altered greenstone occur worldwide; a fresh surface or mineral tests would help distinguish them.
