igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained aphanitic texture, dull to sub-vitreous luster, specific gravity around 2.8 to 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 sub-vitreous luster, specific gravity around 2.8 to 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 crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans, and it is also abundantly found on the surfaces of the Moon, Mars, and Venus.
Field identification & locations
Can be identified by its dark, heavy, fine-grained appearance, often found in stream beds or beaches where wave action has smoothed it into a pebble.
