igneous
Basalt with Weathered Interior
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black fresh surfaces with a fine-grained (aphanitic) texture, weathering to a reddish-brown iron-oxide stained interior, dull to sub-vitreous luster.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black fresh surfaces with a fine-grained (aphanitic) texture, weathering to a reddish-brown iron-oxide stained interior, dull to sub-vitreous luster.
Formation & geological history
Formed by the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic) exposed at or very near the Earth's surface.
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in stonework and 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 color, fine-grained texture, and the characteristic rusty-orange weathering rind visible on fractured surfaces.
