igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale; typically dark grey, black, or dark brown in color; fine-grained or 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; typically dark grey, black, or dark brown in color; fine-grained or 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 basaltic lava exposed at or very near the surface of a planet or moon. Geological age can range from recent volcanic eruptions to billions of years old.
Uses & applications
Used in construction as crushed stone for road bases, concrete aggregate, railroad ballast, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forms much of the volcanic islands worldwide as well as on the Moon and Mars.
Field identification & locations
Found abundantly in marine environments, riverbeds, and beaches where wave and current action has smoothed and rounded the rough volcanic fragments into pebbles.
