igneous
Basalt Pebble
Extrusive igneous rock (Mafic)
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), typically containing plagioclase feldspar, pyroxene, and olivine. Cleavage: None. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), typically containing plagioclase feldspar, pyroxene, and olivine. Cleavage: None. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the Earth's surface, often in volcanic eruptions or oceanic crust formation.
Uses & applications
Used in construction, aggregate for roads, railroad ballast, and sometimes in stonework and monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and also makes up significant portions of volcanic regions on the Moon and Mars.
Field identification & locations
Identified by its dense, dark, fine-grained appearance. Commonly found along beaches, riverbeds, and volcanic regions worldwide.
