igneous
Basalt Pebble
Basalt
Hardness: 6 on Mohs scale; Color: dark gray to black, often with a weathered lighter exterior rim; Luster: dull to sub-vitreous; Texture: fine-grained (aphanitic), rounded and smooth from water erosion.
- Hardness
- 6 on Mohs scale
- Luster
- dull to sub-vitreous
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Physical properties
Hardness: 6 on Mohs scale; Color: dark gray to black, often with a weathered lighter exterior rim; Luster: dull to sub-vitreous; Texture: fine-grained (aphanitic), rounded and smooth from water erosion.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. Subsequent erosion by rivers, lakes, or ocean waves smoothed it into a pebble.
Uses & applications
Commonly used in aggregate for construction, crushed stone for road bases, concrete, and landscape decoration.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming the oceanic crust almost entirely. It is also extremely common on the Moon and Mars.
Field identification & locations
Identified by its dark coloration, heavy density, fine grain, and rounded water-worn shape. Commonly found along riverbeds, beaches, and volcanic terrains.
