igneous
Dark, fine-grained rock fragment (possibly basalt)
Basalt, a plagioclase–pyroxene volcanic rock; identification is uncertain from the photo
AI-generated identification · may be incorrectDark gray to black, dull surface with a few tan patches; likely fine-grained and massive. Basalt commonly has Mohs hardness about 6, plagioclase and pyroxene crystals, and specific gravity around 2.8–3.0; these traits cannot be confirmed visually here.
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Physical properties
Dark gray to black, dull surface with a few tan patches; likely fine-grained and massive. Basalt commonly has Mohs hardness about 6, plagioclase and pyroxene crystals, and specific gravity around 2.8–3.0; these traits cannot be confirmed visually here.
Formation & geological history
If basalt, it formed when mafic lava cooled rapidly at or near Earth’s surface; basalt occurs from ancient to modern volcanic settings.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and building stone; this small fragment has little practical or jewelry value.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also forms much of the ocean floor.
Field identification & locations
A fresh basalt break is typically dark and dense, with crystals too small to distinguish unaided; compare with a hand lens and check for vesicles or visible grains. Found in volcanic regions worldwide.
