igneous
Basalt fragments in a light-colored host rock
Basalt (mafic volcanic rock; chiefly plagioclase, pyroxene, and sometimes olivine)
AI-generated identification · may be incorrectThe dark fragments are fine-grained and appear dull to slightly glassy, with irregular shapes; basalt typically has Mohs hardness 5–6 and specific gravity around 2.8–3.0. The pale material may be a separate host rock or matrix, so its composition cannot be identified from the image alone.
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Physical properties
The dark fragments are fine-grained and appear dull to slightly glassy, with irregular shapes; basalt typically has Mohs hardness 5–6 and specific gravity around 2.8–3.0. The pale material may be a separate host rock or matrix, so its composition cannot be identified from the image alone.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools at or near the surface; the fragments may be volcanic clasts embedded in a lighter rock. No age or precise formation setting can be determined from the photograph.
Uses & applications
Basalt is widely used as crushed aggregate, road material, and building stone; suitable pieces are also collected as geological specimens.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also forms much of the ocean floor.
Field identification & locations
Look for dark, dense, fine-grained fragments, often with tiny crystals or vesicles; field identification is stronger on a fresh, unweathered surface. Basalt occurs worldwide in volcanic regions, but the pictured material needs in-person examination to confirm.
