igneous
Rounded dark cobble, likely basalt
Probable basalt; exact identification cannot be confirmed from the photograph
AI-generated identification · may be incorrectDark gray to brown, fine-grained and dull, with a weathered rounded surface. Basalt is typically Mohs 6, composed mainly of plagioclase and pyroxene, and has no visible cleavage; the image does not reveal its crystal structure or specific gravity.
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Physical properties
Dark gray to brown, fine-grained and dull, with a weathered rounded surface. Basalt is typically Mohs 6, composed mainly of plagioclase and pyroxene, and has no visible cleavage; the image does not reveal its crystal structure 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 volcanic settings. This cobble’s age and history are not identifiable from appearance alone.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and building material; this small cobble is mainly suitable for collecting or decoration.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also makes up much of the ocean floor.
Field identification & locations
Its rounded shape suggests transport by water or abrasion, but the speckled countertop makes the specimen’s texture difficult to assess. A fresh broken surface, hand lens, and simple hardness tests would help distinguish basalt from other dark rocks.
