igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained to aphanitic texture, dull luster, high specific gravity (approx. 2.8 - 3.0)
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained to aphanitic texture, dull luster, high specific gravity (approx. 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 surface of a planet or moon.
Uses & applications
Used in construction as aggregate, in road building, railroad ballast, and sometimes in landscaping or decorative stones.
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, Mars, and Venus.
Field identification & locations
Easily identified by its dark, fine-grained appearance, high density, and smooth, water-worn texture when found in riverbeds or beaches.
