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.
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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.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or 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 dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and is also found abundantly on the Moon, Mars, and Venus.
Field identification & locations
Easily identified by its dark, fine-grained appearance, heavy weight relative to its size, and water-worn smooth shape when found as a pebble.
