igneous
Basalt Pebble
Extrusive Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark black to gray color, fine-grained aphanitic texture, and subconchoidal fracture.
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Physical properties
Hardness of 6 on the Mohs scale, dark black to gray color, fine-grained aphanitic texture, and subconchoidal fracture.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows exposed at or near the Earth's surface.
Uses & applications
Used extensively in construction as crushed aggregate, railroad ballast, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans and also forms extensive volcanic provinces on land.
Field identification & locations
Identified by its dark color, heavy weight, and fine-grained texture; commonly found in riverbeds and beaches where waves have tumbled it smooth.
