igneous
Basalt Pebble
Basalt
Hardness 6 on Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to sub-vitreous luster, specific gravity 2.8-3.0, rounded and smoothed by water action.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to sub-vitreous luster, specific gravity 2.8-3.0, rounded and smoothed by water action.
Formation & geological history
Formed from the rapid cooling of low-viscosity magnesium-rich and iron-rich lava at or near the Earth's surface, later eroded and rounded by stream or beach action into a pebble.
Uses & applications
Used widely as hot massage stones, decorative landscaping pebbles, aquarium gravel, crushed stone for construction aggregate, and railway ballast.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming most of the ocean floors. It is also found extensively on the Moon and Mars.
Field identification & locations
Identified by its heavy weight, dark color, fine grain, and rounded pebble shape. Commonly found on beaches, riverbeds, and volcanic regions worldwide.
