igneous
Basalt Pebble
Basalt
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) or glassy texture, dull to sub-metallic luster, specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) or glassy texture, dull to sub-metallic luster, specific gravity around 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 Earth's surface, often originating from volcanic eruptions.
Uses & applications
Used in construction as crushed stone for road bases, concrete aggregate, railroad ballast, and in the production of basalt fiber.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Easily identified by its dark, dense, fine-grained appearance and rounded shape from water or wave action in riverbeds or beaches.
