igneous
Basalt Pebble
Basalt (Mafic Volcanic Rock)
Hardness: 6.0; Color: Dark grey to black, weathered surfaces can be lighter grey; Luster: Dull or earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black, weathered surfaces can be lighter grey
- Luster
- Dull or earthy
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black, weathered surfaces can be lighter grey; Luster: Dull or earthy; Crystal structure: Aphanitic (fine-grained); 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 specimen appears to be a water-worn river pebble or glacial till.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, railroad ballast, and in ornamental landscaping as decorative river rock.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up the majority of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identified in the field by its dark color, heavy weight (relative to size), and fine-grained texture. Commonly found in former volcanic regions or distributed by river and glacial transport.
