igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale; dark gray to black color; fine-grained aphanitic luster; plagioclase feldspar and pyroxene mineral structure; specific gravity around 2.9.
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Physical properties
Hardness 6 on Mohs scale; dark gray to black color; fine-grained aphanitic luster; plagioclase feldspar and pyroxene mineral 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
Used heavily in construction as crushed aggregate for roads, railroad ballast, and in the production of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forms massive volcanic formations like the Giant's Causeway.
Field identification & locations
Identified by its dark, fine-grained matrix and heavy weight; found globally in volcanic regions and oceanic crust.
