igneous
Basalt Pebble
Extrusive Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline structure, and high specific gravity.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline structure, and high specific gravity.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or near the Earth's surface.
Uses & applications
Used in construction aggregates, road base, asphalt, and railroad ballast.
Geological facts
Basalt is the most common rock type in the Earth's crustal portions underlying the ocean basins and also forms much of the lunar maria.
Field identification & locations
Easily identified by its dark, fine-grained appearance and heavy weight relative to its size; commonly found in riverbeds and beaches.
