igneous
Basalt Pebble
Extrusive igneous rock
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing microscopic crystals. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
Explore Basalt Pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing microscopic crystals. Specific gravity: 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. Geological age varies widely from recent volcanic activity to billions of years old.
Uses & applications
Used in construction, aggregate, road base, riprap, and occasionally in polished decorative items or hot stone massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forming much of the volcanic islands such as the Hawaiian archipelago.
Field identification & locations
Can be identified in the field by its dark, fine-grained appearance, high density, and smooth, weathered shape common in riverbeds and beaches.
