igneous
Basalt River Stone
Basalt
Hardness: 5-6 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8-3.0
- Hardness
- 5-6 Mohs
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); 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. This specific specimen has been Rounded by fluvial (river) erosion.
Uses & applications
Commonly used in construction as aggregate, for road base, in hot stone massage therapy, and as decorative landscaping stones.
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 extensively on the Moon and Mars.
Field identification & locations
Look for a heavy, dark-colored, fine-grained rock that feels dense. Often found in riverbeds or near volcanic regions worldwide. Small rounded pebbles are ubiquitous in garden centers.
