igneous
Basalt River Pebble
Basalt (Mafic volcanic rock)
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull or earthy; Structure: Aphanitic (fine-grained), often vesicular or amygdaloidal in larger samples; Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull or earthy
Identified More igneous →
Explore Basalt River Pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull or earthy; Structure: Aphanitic (fine-grained), often vesicular or amygdaloidal in larger samples; Specific Gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been rounded and smoothed by water erosion (alluvial process) in a river or stream bed.
Uses & applications
Used primarily as aggregate in construction, road base, and landscaping. Polished pebbles are used in decor and massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight compared to other pebbles, and fine-grained texture. Commonly found in volcanic regions and riverbeds downstream from volcanic mountains.
