igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull luster, aphanitic fine-grained crystal structure, specific gravity around 2.9.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, aphanitic fine-grained crystal structure, specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the Earth's surface.
Uses & applications
Widely used in construction for crushed stone, road base, concrete aggregate, and sometimes as dimension stone or architectural tiles.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also forms massive volcanic structures like the Giant's Causeway.
Field identification & locations
Identify by its dark color, fine-grained texture, and heavy weight relative to size. Found globally in volcanic regions and ocean floors.
