igneous
Basalt (Vesicular/Amygdaloidal or Water-Worn)
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to waxy; Texture: Fine-grained (aphanitic) with small vesicles or inclusions; SG: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to waxy
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to waxy; Texture: Fine-grained (aphanitic) with small vesicles or inclusions; SG: 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 particular specimen shows rounding consistent with river or coastal water erosion.
Uses & applications
Primary use is in construction as road base, concrete aggregate, and railroad ballast. Smooth river stones of basalt are also used in hot stone massage and decorative landscaping.
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, Mars, and Venus.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine texture. This specimen may contain amygdales (filled gas bubbles). Commonly found in volcanic regions, oceanic islands, and riverbeds.
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