igneous
Rounded gray pebble, likely andesite or basalt
Fine-grained volcanic rock; composition likely plagioclase feldspar, pyroxene, and possibly amphibole
AI-generated identification · may be incorrectGray-green, dull to faintly satin luster, fine-grained, massive, and rounded by abrasion; Mohs hardness about 6, with no obvious cleavage. Exact identification requires a fresh surface or testing.
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Physical properties
Gray-green, dull to faintly satin luster, fine-grained, massive, and rounded by abrasion; Mohs hardness about 6, with no obvious cleavage. Exact identification requires a fresh surface or testing.
Formation & geological history
Likely weathered from an extrusive volcanic flow and rounded in a stream, beach, or gravel deposit; volcanic rocks of this kind range from recent to hundreds of millions of years old.
Uses & applications
Used as aggregate, road gravel, landscaping stone, and occasionally as a decorative or lapidary material; this small ordinary pebble has minimal commercial value.
Geological facts
The subtle lighter band or seam may be a mineral vein, weathering boundary, or fracture fill rather than layering. Its rounded shape reflects transport and abrasion, not its original volcanic form.
Field identification & locations
Look for tiny interlocking crystals, a fine-grained texture, and a dark gray color; basalt is generally darker and denser, while andesite is commonly medium gray. Common in volcanic regions and river or glacial gravels.
