igneous
Rounded fine-grained gray pebble, likely basalt
Basalt (tentative identification; image alone cannot confirm composition)
AI-generated identification · may be incorrectDark gray, fine-grained, dull to slightly sparkly surface, with no visible crystals or cleavage. Typical basalt hardness is about 6 on the Mohs scale and specific gravity about 2.8–3.0.
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Physical properties
Dark gray, fine-grained, dull to slightly sparkly surface, with no visible crystals or cleavage. Typical basalt hardness is about 6 on the Mohs scale and specific gravity about 2.8–3.0.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface; it occurs in volcanic settings from ancient to recent ages. Its rounded shape suggests abrasion during transport by water or sediment.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and construction material; this small pebble is mainly a natural-history or decorative specimen.
Geological facts
Basalt is one of Earth’s most abundant volcanic rocks and also makes up much of the lunar maria.
Field identification & locations
The fine grain and dark gray color fit basalt, but other fine-grained rocks can look similar; a fresh broken surface and mineral or chemical testing help confirm it. Basalt is common in volcanic regions and river or beach gravels.
