igneous
Polished black stone, possibly basalt
Likely fine-grained basalt; exact identification is uncertain from the image alone.
AI-generated identification · may be incorrectDark gray to black, smooth and glossy from polishing, with scattered pits or inclusions; basalt is typically composed of plagioclase and pyroxene, Mohs hardness about 6, and has no visible cleavage.
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Physical properties
Dark gray to black, smooth and glossy from polishing, with scattered pits or inclusions; basalt is typically composed of plagioclase and pyroxene, Mohs hardness about 6, and has no visible cleavage.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools at or near Earth's surface; specimens can range from recent to billions of years old.
Uses & applications
Could be a decorative or tumbled stone; basalt is widely used as aggregate, paving stone, and construction material.
Geological facts
Basalt is one of Earth's most common volcanic rocks and also forms much of the ocean floor.
Field identification & locations
The rounded, polished shape and image provide few diagnostic details; check for a fine-grained interior and test hardness to distinguish basalt from other dark stones. Basalt occurs worldwide in volcanic regions.
