igneous
Dark river-worn rock, possibly basalt
Basalt (tentative; visual identification is uncertain)
AI-generated identification · may be incorrectRounded, dark gray to black, fine-grained and dull to slightly glossy; likely Mohs 5–6, with no visible crystals or cleavage. The image alone cannot confirm its composition or specific gravity.
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Physical properties
Rounded, dark gray to black, fine-grained and dull to slightly glossy; likely Mohs 5–6, with no visible crystals or cleavage. The image alone cannot confirm its composition or specific gravity.
Formation & geological history
If basalt, it formed when mafic lava cooled rapidly at or near Earth’s surface; basalt occurs from ancient to recent geological ages. Its smooth rounded shape suggests abrasion during transport by water.
Uses & applications
Common basalt is used as aggregate, paving stone, and landscaping material; this unverified pebble has little commercial value.
Geological facts
Basalt is rich in plagioclase and pyroxene, often with olivine, but those minerals are not identifiable in this photograph.
Field identification & locations
A dense, fine-grained dark rock with no obvious layering is consistent with basalt; compare its heft and inspect a fresh broken surface to distinguish it from other dark rocks. Basalt is widespread in volcanic regions and river gravels.
