igneous
Basalt
Basalt (Mafic Extrusive Igneous Rock)
Mohs hardness around 6; dark gray to black; dull to sub-vitreous luster; fine-grained (aphanitic) texture; specific gravity 2.8-3.0; composed mostly of plagioclase feldspar and pyroxene
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Physical properties
Mohs hardness around 6; dark gray to black; dull to sub-vitreous luster; fine-grained (aphanitic) texture; specific gravity 2.8-3.0; composed mostly of plagioclase feldspar and pyroxene
Formation & geological history
Formed from the rapid cooling of low-viscosity mafic lava exposed at or very near the Earth's surface, commonly found in oceanic crust and volcanic regions
Uses & applications
Widely used in construction as crushed stone, aggregate in concrete, road base, asphalt, and as cast basalt for wear-resistant liners
Geological facts
Basalt is the most common rock type in the Earth's crust, forming virtually all oceanic crust and vast continental flood basalt provinces like the Deccan Traps
Field identification & locations
Identified by its fine grain size, heavy density, and dark color; easily found in volcanic zones, beaches near volcanic islands, and gravel quarries; low value due to abundance
