igneous
Tumbled dark pebble, likely basalt with pale mineral veins
Basalt (tentative); pale veins may be quartz or calcite
AI-generated identification · may be incorrectRounded, polished, dark gray to black with thin pale veins. Basalt is typically fine-grained, Mohs hardness about 5–6, and has no visible crystal faces; the photo alone cannot confirm its composition or specific gravity.
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Physical properties
Rounded, polished, dark gray to black with thin pale veins. Basalt is typically fine-grained, Mohs hardness about 5–6, and has no visible crystal faces; the photo alone cannot confirm its composition or specific gravity.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface; it occurs from ancient to recent volcanic settings. The veins formed later as mineral-rich fluids filled fractures, and tumbling smoothed the pebble.
Uses & applications
Primarily a decorative or collectible stone; basalt is also widely used as aggregate, paving, and construction stone.
Geological facts
Dark color and pale fracture-filling veins are consistent with basalt, but similar pebbles can be other dark rocks such as andesite or metamorphic stone.
Field identification & locations
A definitive field identification needs a fresh surface, texture inspection, and simple hardness tests; basalt commonly occurs in volcanic regions and river or beach gravels derived from them.
