igneous
Rounded dark river pebble
Likely basalt or fine-grained mafic volcanic rock; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray-green, smooth and water-worn, dull to faintly satin luster, fine-grained with no visible crystals or cleavage. Estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1 if basaltic.
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Physical properties
Dark gray-green, smooth and water-worn, dull to faintly satin luster, fine-grained with no visible crystals or cleavage. Estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1 if basaltic.
Formation & geological history
Probably eroded from a basaltic lava flow and rounded by stream, beach, or glacial transport; its geological age cannot be determined visually and may range from ancient to recent.
Uses & applications
Suitable mainly as a decorative pebble, craft material, or small landscaping stone; it has little commercial value unless unusually attractive or locally significant.
Geological facts
The rounded shape reflects abrasion during transport, while the dark color commonly indicates iron- and magnesium-rich minerals such as pyroxene and olivine.
Field identification & locations
Common in volcanic regions, river gravels, beaches, and glacial deposits worldwide. A fresh broken surface, streak-free hardness test, and lack of visible layering would support basalt; a magnet test may show weak attraction.
