igneous
Basalt Pebble
Mafic Extrusive Igneous Rock
Hardness: 6 on Mohs scale, Color: Dark grey to greenish-black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific gravity: 2.8-3.0
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Physical properties
Hardness: 6 on Mohs scale, Color: Dark grey to greenish-black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction as crushed stone, aggregate in concrete, railroad ballast, and in the manufacturing 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 also makes up extensive volcanic formations on the Moon and Mars.
Field identification & locations
Identified by its dark, fine-grained appearance, often heavily weathered and rounded into smooth pebbles by water action in rivers or beaches.
