igneous
Rounded weathered stone
Indeterminate; likely a fine-grained mafic rock such as basalt or andesite
AI-generated identification · may be incorrectGray-brown, dull to weakly earthy luster, rounded and moderately weathered; likely hardness about 5–6 Mohs, with no visible cleavage or crystals. Exact identification requires testing for streak, magnetism, density, and thin-section texture.
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Physical properties
Gray-brown, dull to weakly earthy luster, rounded and moderately weathered; likely hardness about 5–6 Mohs, with no visible cleavage or crystals. Exact identification requires testing for streak, magnetism, density, and thin-section texture.
Formation & geological history
Probably a naturally water-worn cobble formed from volcanic rock and rounded in a stream, beach, or glacial environment; its geological age cannot be determined from the photograph.
Uses & applications
Commonly used as a decorative or landscaping stone, paperweight, or teaching specimen; no significant gem value is apparent.
Geological facts
The smooth shape reflects abrasion during transport, while the mottled surface may result from weathering or iron-bearing minerals. The image does not show diagnostic features sufficient for a precise species-level identification.
Field identification & locations
Common in volcanic terrains and river gravels worldwide; inspect a fresh broken surface for fine grain, test magnetism, and use dilute hydrochloric acid to check for carbonate coating. Estimated value: $1–$10 as an ordinary cobble, or under $20 if locally significant.
