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-vitreous 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-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 Earth's surface, often rounded by water action in riverbeds or beaches.
Uses & applications
Used in construction, aggregate, road base, and landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Commonly found in river gravels and volcanic regions worldwide; identified by its dark, dense, fine-grained appearance.
