igneous
Basalt Pebble
Aphanitic mafic extrusive rock
AI-generated identification · may be incorrectHardness 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to cryptocrystalline structure, high specific gravity.
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Physical properties
Hardness 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to cryptocrystalline structure, high specific gravity.
Formation & geological history
Formed from the rapid cooling of low-viscosity mafic lava flows at the Earth's surface.
Uses & applications
Used in construction as crushed aggregate, railroad ballast, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also forms extensive continental flood basalts.
Field identification & locations
Identify by its dark, fine-grained matrix and smooth water-worn surface found near riverbeds or beaches; common worldwide.
