igneous
Basalt
Extrusive mafic igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale; dark gray to black color; sub-to-aphanitic luster; fine-grained or glassy crystal structure; specific gravity 2.8-3.0.
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Physical properties
Hardness 6 on Mohs scale; dark gray to black color; sub-to-aphanitic luster; fine-grained or glassy crystal structure; specific gravity 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Used extensively in construction as crushed stone for road bases, concrete aggregate, and in the production of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and forms most of the Hawaiian islands.
Field identification & locations
Identified by its dark color, fine-grained texture, and heavy weight relative to its size; commonly found in volcanic regions worldwide.
