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 - 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 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the Earth's surface, often from volcanic eruptions
Uses & applications
Used in construction, road aggregate, railroad ballast, and sometimes in manufacturing stone wool insulation
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins, and it is also found extensively on the Moon and Mars
Field identification & locations
Identified by its dark coloration, heavy weight relative to size, and fine-grained matrix; easily found in volcanic regions, riverbeds, and beaches worldwide
