igneous
Basalt River Stone
Basalt (Mafic Igneous Rock)
Hardness: 6-7 (Mohs); Color: Dark grey to greenish-grey; Luster: Dull/Matte; Structure: Fine-grained (aphanitic), massive; Cleavage: None; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to greenish-grey
- Luster
- Dull/Matte
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to greenish-grey; Luster: Dull/Matte; Structure: Fine-grained (aphanitic), massive; Cleavage: None; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. These specific specimens were rounded by water erosion in a river or coastal environment.
Uses & applications
Commonly used in construction (crushed stone), landscaping, high-quality road base, and for hot stone massage therapy due to heat retention.
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 relative to size, dark color, and fine-grained texture with no visible crystals to the naked eye. Often found as rounded cobbles in riverbeds and on volcanic beaches.
