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 around 2.9.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline to aphanitic structure, specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Widely used in construction, crushed stone for road bases, railroad ballast, and manufacturing of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and forms spectacular columnar jointing structures like the Giant's Causeway.
Field identification & locations
Identify by its dark, fine-grained appearance and heavy weight relative to its size; found globally in volcanic regions and oceanic crusts.
