igneous
Basalt Riverstone
Basalt (Aphanitic Mafic Volcanic Rock)
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when wet; Crystal Structure: Fine-grained (Aphanitic); Cleavage: None/Irregular; Specific Gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic when wet
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when wet; Crystal Structure: Fine-grained (Aphanitic); Cleavage: None/Irregular; 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 specimen has been water-worn and smoothed in a river or coastal environment, likely during the Quaternary period.
Uses & applications
Commonly used as aggregate in construction, road base, and for high-quality decorative landscaping. Polished stones are used in hot stone massage therapy and minor jewelry/craft projects.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is også found on the Moon and Mars.
Field identification & locations
Identify by its heavy weight relative to size, dark uniform color, and lack of visible large crystals. Most common in volcanic regions and riverbeds downstream from volcanic plateaus.
