igneous
Basalt River Pebble
Basalt
Hardness: 5-6 Mohs. Color: dark grey to charcoal. Luster: dull/earthy. Structure: fine-grained (aphanitic). Cleavage: none. Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark grey to charcoal
- Luster
- dull/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 grey to charcoal. Luster: dull/earthy. Structure: fine-grained (aphanitic). Cleavage: none. Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. Extrusive volcanic origin. This specimen has been rounded by fluvial (river) or coastal erosion.
Uses & applications
Used widely in construction as crushed aggregate, for road base, concrete, and as decorative landscaping stones.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals. Commonly found in riverbeds, volcanic regions, and gravel pits.
