igneous
Basalt Pebble
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6-7 on Mohs scale; Color: dark gray to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), microscopic mineral grains; Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- dark gray to black
- Luster
- dull to earthy
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: 6-7 on Mohs scale; Color: dark gray to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), microscopic mineral grains; Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity mafic lava at or near the Earth's surface, typically at mid-ocean ridges, oceanic islands, or continental flood basalt provinces. Smooth rounded shape created by water erosion in rivers or ocean waves.
Uses & applications
Commonly used as crushed stone for construction, road base, concrete aggregate, landscaping pebbles, hot stone massage therapy, and general decorative rock.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up almost the entire ocean floor. It is also extremely common on the Moon (lunar maria) and Mars.
Field identification & locations
Identified by its dark color, heavy density, fine-grained texture, and smooth rounded pebble form from stream or beach erosion. Very common globally along coasts, riverbeds, and volcanic regions.
