igneous
Basalt Pebble
Mafic Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, typically dark gray to black in color, fine-grained to aphanitic texture, dull to sub-vitreous luster, specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, typically dark gray to black in color, fine-grained to aphanitic texture, dull to sub-vitreous 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 surface of a planet or moon, often wave-smoothed into a pebble.
Uses & applications
Used in construction, as aggregate in concrete, road base, and occasionally in landscaping or decorative paving.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans, and it is also extensively found on the Moon and Mars.
Field identification & locations
Found worldwide along beaches, riverbeds, and volcanic regions; easily identified by its dark color, heavy weight relative to size, and fine-grained texture.
