igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained aphanitic texture, dull to submetallic 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 texture, dull to submetallic luster, specific gravity around 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, road aggregate, railroad ballast, and decorative landscaping.
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
Found commonly in beaches, riverbeds, and volcanic regions worldwide; identified by its dark, heavy, and fine-grained appearance often rounded by water action.
