igneous
Dark volcanic rock fragment (possibly basalt)
Basalt, a fine-grained mafic volcanic rock; identification is uncertain from the image
AI-generated identification · may be incorrectSmall, dark gray-to-black, irregular fragment with a dull to slightly shiny surface and a few lighter grains. Basalt is typically Mohs 6, composed mainly of plagioclase and pyroxene, and has no visible cleavage.
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Physical properties
Small, dark gray-to-black, irregular fragment with a dull to slightly shiny surface and a few lighter grains. Basalt is typically Mohs 6, composed mainly of plagioclase and pyroxene, and has no visible cleavage.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools quickly at or near Earth’s surface. Basalt ranges from geologically recent lava flows to ancient oceanic crust; this fragment’s age and origin cannot be determined visually.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and building material; this small fragment has little practical or gem value.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and makes up much of the ocean floor.
Field identification & locations
A dark, dense, fine-grained appearance supports basalt, but a closer view or tests are needed to distinguish it from other dark rocks. Basalt is common in volcanic regions and on oceanic islands.
