igneous
Dark volcanic rock (likely basalt)
Basalt, a fine-grained mafic volcanic rock; visual identification is tentative
AI-generated identification · may be incorrectDark gray to black, dull, fine-grained and irregular; likely composed mainly of plagioclase and pyroxene, possibly olivine. Typical basalt has Mohs hardness around 6, but crystal structure and exact properties cannot be confirmed from the image.
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Physical properties
Dark gray to black, dull, fine-grained and irregular; likely composed mainly of plagioclase and pyroxene, possibly olivine. Typical basalt has Mohs hardness around 6, but crystal structure and exact properties cannot be confirmed from the image.
Formation & geological history
Forms when iron- and magnesium-rich lava cools rapidly at or near the surface; basalt ranges from ancient to actively forming and is common at volcanic fields and ocean floors.
Uses & applications
Used as crushed aggregate, road stone, construction material, and occasionally as a decorative or collectible specimen.
Geological facts
Basalt is Earth’s most widespread volcanic rock and makes up much of the oceanic crust.
Field identification & locations
The specimen’s dark color and massive, fine-grained appearance fit basalt, but a close-up or fresh surface is needed to distinguish it from other dark rocks. Common in volcanic regions worldwide.
