igneous
Basalt Pebble
Extrusive Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, fine-grained aphanitic texture, and dull to sub-metallic luster.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained aphanitic texture, and dull to sub-metallic luster.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface.
Uses & applications
Used widely in construction aggregates, road base, railroad ballast, and sometimes as tumbled decorative stones.
Geological facts
Basalt is the most common rock type in the Earth's crustal portions underlying the world's ocean basins.
Field identification & locations
Easily identified by its dark, dense, fine-grained appearance, often found smoothly water-worn in riverbeds and coastlines.
