igneous
Basalt Pebble
Aphanitic Mafic Igneous Rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline or glassy crystal structure, specific gravity 2.8 to 3.0.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, microcrystalline or glassy crystal structure, specific gravity 2.8 to 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Used widely in construction as crushed aggregate, railroad ballast, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also forms extensive volcanic provinces on the Moon and Mars.
Field identification & locations
Identified by its fine-grained, dark appearance and heavy weight relative to its size; commonly found in riverbeds and beaches.
