igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained aphanitic texture, dull to sub-metallic luster, 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, fine-grained aphanitic texture, dull to sub-metallic luster, specific gravity around 2.8-3.0.
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 in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in landscaping.
Geological facts
Basalt is the most common rock type on Earth's crust, primarily making up the ocean floors and forming famous geological formations like the Giant's Causeway.
Field identification & locations
Identified by its dark color, fine-grained texture, and high density; commonly found in riverbeds and beaches where water action has smoothed it into a pebble.
