igneous
Weathered gray pebble
Likely fine-grained basalt or andesite; exact identification requires testing
AI-generated identification · may be incorrectDark gray-brown, dull to weakly earthy luster, massive and fine-grained with no visible crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.0.
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Physical properties
Dark gray-brown, dull to weakly earthy luster, massive and fine-grained with no visible crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.0.
Formation & geological history
Probably a naturally weathered volcanic rock formed when lava cooled rapidly, generally in the Cenozoic or older; its rounded shape indicates transport by water, ice, or sediment.
Uses & applications
Common varieties have little collector value but may be used as landscaping stone, aggregate, road material, or teaching specimens.
Geological facts
The pale patch may be weathering, alteration, or a different mineral-rich surface rather than a distinct gemstone feature.
Field identification & locations
Common in volcanic terrains and stream or beach gravels worldwide; a streak, hardness, magnetism, and fresh broken surface would help distinguish basalt from andesite or other dark rocks.
