igneous
Basalt River Stone
Aphanitic Basalt
Hardness: 5-6 (Mohs); Color: Dark grey to black or dark brown; Luster: Dull/Earthy; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to black or dark brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black or dark brown; Luster: Dull/Earthy; 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 near the Earth's surface. Often rounded into smooth pebbles by water erosion in riverbeds or coastal areas.
Uses & applications
Used in landscaping, decorative stone, aquarium decor, hot stone massage therapy, and construction aggregate.
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 by its heavy weight (high density), dark matte color, and lack of visible crystals. It is commonly found in volcanic regions or transported to riverbanks.
