igneous
River Stone (Basalt)
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6 on Mohs scale; Color: Dark grey to charcoal; Luster: Dull/Earthy; Crystal structure: Path-microcrystalline (fine-grained); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to charcoal
- Luster
- Dull/Earthy
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to charcoal; Luster: Dull/Earthy; Crystal structure: Path-microcrystalline (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 specific specimen has been smoothed and rounded over time by water erosion in a river or coastal environment.
Uses & applications
Used widely in construction as aggregate, road base, and concrete. Smooth river specimens are used in landscaping, massage therapy (hot stones), and as decorative accents.
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 on the Moon and Mars.
Field identification & locations
Identify in the field by its heavy weight (density), dark color, and lack of visible large crystals. Commonly found in volcanic regions, riverbeds, and glacial deposits.
