igneous
Basalt River Stone
Basaltic Igneous Rock
Hardness: 6 on Mohs scale; Color: Dark grey to dull black; Luster: Dull or earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8 to 3.0. This specimen shows a smooth, water-worn texture.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to dull black
- Luster
- Dull or earthy
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to dull black; Luster: Dull or earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8 to 3.0. This specimen shows a smooth, water-worn texture.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This particular specimen has been naturally tumbled and smoothed by river or coastal water movement.Basalt is found throughout Earth's history, especially in oceanic crust.
Uses & applications
Basalt is used extensively in construction as aggregate, for road base, and in concrete. River-worn basalt is popular in landscaping, aquarium decor, and as massage stones.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon (the dark lunar Maria) and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine-grained texture. It often shows smooth, rounded edges if found in water environments. Found globally in volcanic regions and riverbeds downstream from volcanic sources.
