igneous
Basalt Pebble
Extrusive Igneous Rock / Basalt
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8-3.0
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Physical properties
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction, aggregate, road base, and occasionally in decorative landscaping or as tumbled stones.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans, and it is also the primary rock type found on the lunar maria and the surface of Mars.
Field identification & locations
Found globally in volcanic regions, oceanic islands, and ancient lava flows. Easily identified by its dark, fine-grained appearance, water-worn smooth texture in rivers or beaches, and high density.
