igneous
Basalt Pebble
Aphanitic mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline structure, and high specific gravity around 2.9.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline structure, and high specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Commonly used in construction aggregate, railroad ballast, and landscaping stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forming much of the moon's maria.
Field identification & locations
Identified by its fine-grained dark matrix, often rounded into smooth pebbles by water action in riverbeds or coastal beaches.
