igneous
Polished gray stone pebble
Likely fine-grained basalt or andesite; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray, opaque, fine-grained, and weakly speckled with a dull-to-subtle vitreous polish; likely hardness 5–6 Mohs, with no visible cleavage and an aggregate crystalline texture. Specific gravity is probably about 2.7–3.0.
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Physical properties
Dark gray, opaque, fine-grained, and weakly speckled with a dull-to-subtle vitreous polish; likely hardness 5–6 Mohs, with no visible cleavage and an aggregate crystalline texture. Specific gravity is probably about 2.7–3.0.
Formation & geological history
Probably a naturally rounded volcanic rock later polished or tumbled; basalt commonly formed from rapidly cooled lava, generally from the Cenozoic or older. The smooth circular form indicates human processing rather than natural outcrop shape.
Uses & applications
Used as a decorative tumbled stone, craft material, paperweight, or cabochon-like object; not typically valuable as jewelry unless it has unusual patterning.
Geological facts
Basalt is dominated by plagioclase and pyroxene, sometimes with olivine or magnetite. Its dark color reflects abundant iron- and magnesium-rich minerals.
Field identification & locations
Identify by its fine grain, dark gray color, high density, and lack of large crystals; a streak, magnet test, and close examination of an unpolished edge would help distinguish basalt from slate, concrete, or slag. Common worldwide in volcanic regions and river gravels.
