igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), microscopic crystals. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on 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 Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), microscopic crystals. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed by the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface. Rounded through natural water and wave action tumbling it in rivers or shorelines.
Uses & applications
Used in construction, aggregate for concrete, road base, landscaping, and historically for stone tools and paving.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also found extensively on the Moon and Mars.
Field identification & locations
Easily identified by its heavy weight relative to size, dark gray color, and fine-grained texture. Commonly found in riverbeds, beaches, and volcanic regions worldwide.
