igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained aphanitic texture, dull to sub-vitreous 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 in color, fine-grained aphanitic texture, dull to sub-vitreous luster, specific gravity around 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the Earth's surface, typically originating from volcanic eruptions.
Uses & applications
Used in construction as crushed aggregate, railroad ballast, dimension stone, and in the production of rock wool insulation.
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 and weathered, smooth texture from water tumbling; found worldwide in volcanic provinces and riverbeds.
