igneous
Basalt Pebble
Extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline or aphanitic structure, high specific gravity.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline or aphanitic structure, high specific gravity.
Formation & geological history
Formed from the rapid cooling of mafic lava flows at Earth's surface, typically volcanic in origin.
Uses & applications
Used in construction aggregates, railroad ballast, and decorative landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust beneath the oceans and also forms the maria on the Moon.
Field identification & locations
Identify by its dark color, fine-grained texture, and heavy feel; commonly found in riverbeds and beaches where volcanic rocks erode.
