igneous
Likely basalt (dark volcanic rock)
Basalt; a fine-grained mafic rock composed chiefly of plagioclase and pyroxene, commonly with olivine
AI-generated identification · may be incorrectDark gray to black, dull to slightly vitreous; typically fine-grained and dense, with Mohs hardness about 5–6 and no distinct cleavage. The photograph is unclear, so texture and mineral identification cannot be confirmed.
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Physical properties
Dark gray to black, dull to slightly vitreous; typically fine-grained and dense, with Mohs hardness about 5–6 and no distinct cleavage. The photograph is unclear, so texture and mineral identification cannot be confirmed.
Formation & geological history
Forms when iron- and magnesium-rich lava cools at or near the surface; basalt occurs from ancient to geologically recent eruptions.
Uses & applications
Used as crushed aggregate, road stone, and construction material; attractive pieces may be collected or used decoratively.
Geological facts
Basalt is one of Earth’s most abundant volcanic rocks and makes up much of the ocean floor.
Field identification & locations
Look for a dark, dense rock with a fine-grained texture; visible crystals or vesicles can occur. Common at volcanic regions and in ancient lava flows.
