igneous
Basalt or Slag
Extrusive Igneous Rock / Industrial Slag
Hardness varies from 5 to 6 on the Mohs scale depending on composition; color is dark gray to black; luster is dull to vitreous; texture is fine-grained, aphanitic, or vesicular with white mineral inclusions.
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Physical properties
Hardness varies from 5 to 6 on the Mohs scale depending on composition; color is dark gray to black; luster is dull to vitreous; texture is fine-grained, aphanitic, or vesicular with white mineral inclusions.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava exposed at or near the surface of a planet or moon, or as a byproduct of smelting ore.
Uses & applications
Used in construction as crushed stone, aggregate in concrete, and for making stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans and is also found abundantly on the Moon and Mars.
Field identification & locations
Can be identified in the field by its dark color, fine grain, and heavy density relative to its size.
