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, aphanitic crystal structure, high specific gravity.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, aphanitic crystal structure, 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, railroad ballast, stone wool insulation, and occasionally in polished decorative items.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also forms major volcanic features on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance and heavy weight. Commonly found in riverbeds and beaches from ancient volcanic flows.
