igneous
Fine-grained dark rock, possibly basalt
Likely basalt; exact identification is uncertain from the image alone
AI-generated identification · may be incorrectDark brown to black, dull to slightly earthy luster, with a fine-grained appearance and irregular fracture. Basalt typically has Mohs hardness around 6 and specific gravity about 2.8–3.0; individual minerals are not clear enough to assess here.
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Physical properties
Dark brown to black, dull to slightly earthy luster, with a fine-grained appearance and irregular fracture. Basalt typically has Mohs hardness around 6 and specific gravity about 2.8–3.0; individual minerals are not clear enough to assess here.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface. Basalt occurs in volcanic settings of many ages.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and building stone; this specimen appears to be an unworked hand sample.
Geological facts
Basalt commonly contains plagioclase feldspar and pyroxene, sometimes with olivine. Its fine grain reflects rapid cooling that prevented large crystals from growing.
Field identification & locations
A dark, dense, fine-grained texture supports basalt, but the photo does not establish its composition; a fresh surface and simple hardness or streak tests would help. Basalt is widespread in volcanic regions and oceanic crust.
