igneous
Basalt Pebble
Aphanitic Mafic Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to cryptocrystalline structure, specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to cryptocrystalline structure, specific gravity around 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at or near the Earth's surface.
Uses & applications
Used widely in construction as crushed stone for aggregate, railroad ballast, and in the manufacture of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and forms much of the volcanic islands like Hawaii.
Field identification & locations
Easily identified in the field by its dark, fine-grained appearance and smooth, water-worn texture when found in riverbeds or beaches.
