igneous
Basalt River Stone
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull/Matte; Crystal Structure: Fine-grained (aphanitic); Cleavage: None; Shape: Water-worn/smooth
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull/Matte; Crystal Structure: Fine-grained (aphanitic); Cleavage: None; Shape: Water-worn/smooth
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 has been rounded by fluvial (river) or coastal erosion processes.
Uses & applications
Commonly used in landscaping, as aquarium decor, in 'hot stone' massage therapy, and as a primary raw material for industrial aggregate and asphalt.
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 extremely common on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (high density), and lack of visible large crystals. Most common in volcanic regions or riverbeds downstream from volcanic mountain ranges.
