igneous
Basalt
Extrusive mafic igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline to aphanitic structure, specific gravity 2.8-3.0.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline to aphanitic structure, specific gravity 2.8-3.0.
Formation & geological history
Formed by the rapid cooling of low-viscosity, iron- and magnesium-rich lava flows at the Earth's surface.
Uses & applications
Used widely in construction as crushed stone for road bases, concrete aggregate, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming the primary rock of oceanic crust and volcanic islands like Hawaii.
Field identification & locations
Identify by its dark color, fine-grained texture, and heavy weight relative to its size.
