igneous
Basalt Pebble
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6 on the Mohs scale. Color: Dark grey to black, dull earthy luster, fine-grained (aphanitic) texture, dense, no distinct cleavage.
- Hardness
- 6 on the Mohs scale
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark grey to black, dull earthy luster, fine-grained (aphanitic) texture, dense, no distinct cleavage.
Formation & geological history
Formed from the rapid cooling of low-viscosity magnesium- and iron-rich lava at or near the Earth's surface. Rounded by river or ocean erosion into a smooth beach/river pebble.
Uses & applications
Used widely in construction as crushed stone, concrete aggregate, railroad ballast, and for stone carving or aquascaping.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the oceanic floor. It is also extremely common on the Moon and Mars.
Field identification & locations
Identified by its dark color, heavy weight relative to size, fine-grained texture, and smooth rounded pebble shape from water erosion. Found abundantly on beaches, riverbeds, and volcanic areas worldwide.
