igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale; dark gray to black in color; dull to sub-vitreous luster; fine-grained aphanitic crystal structure; high 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; dull to sub-vitreous luster; fine-grained aphanitic crystal structure; high 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 surface of a planet or moon
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in landscaping
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, often smoothed into rounded pebbles by water action in riverbeds or beaches; found worldwide
