igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, typically dark gray to black in color, dull to sub-vitreous luster, aphanitic (fine-grained) crystal structure, no prominent cleavage, specific gravity of 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, typically dark gray to black in color, dull to sub-vitreous luster, aphanitic (fine-grained) crystal structure, no prominent cleavage, specific gravity of 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface.
Uses & applications
Used in construction, aggregate for road building, production of rock wool insulation, and occasionally as decorative stones.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and also makes up significant volcanic formations on the Moon and Mars.
Field identification & locations
Can be identified in the field by its dark color, heavy feel for its size, and fine-grained texture; commonly found in river beds, beaches, and volcanic regions.
