igneous
Rounded fine-grained dark pebble
Likely basalt or basaltic volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectDark gray-green, dull to faintly granular, with a weathered rounded surface and no visible crystals. Likely Mohs hardness about 5–6, massive texture, and specific gravity roughly 2.8–3.1; cleavage absent.
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Physical properties
Dark gray-green, dull to faintly granular, with a weathered rounded surface and no visible crystals. Likely Mohs hardness about 5–6, massive texture, and specific gravity roughly 2.8–3.1; cleavage absent.
Formation & geological history
Probably a naturally water-worn basaltic pebble formed from cooled mafic lava, commonly of Cenozoic or older age. Its smooth shape reflects transport in a stream, beach, or gravel deposit.
Uses & applications
Ordinary pieces have negligible commercial value; basalt is widely used as aggregate, road stone, riprap, and occasionally as decorative stone.
Geological facts
The greenish tone may reflect alteration minerals such as chlorite, epidote, or weathered iron-bearing minerals. The image cannot reliably distinguish basalt from fine-grained andesite, greenstone, or industrial slag.
Field identification & locations
Look for a dense, nonporous stone, faint dark crystals, and a gray-black streak; a magnet may show weak attraction. Acid reaction should be absent, while a steel file typically scratches weakly or not at all; common worldwide in volcanic and gravel regions.
