igneous
Vesicular Basalt
Basalt (a mafic extrusive igneous rock)
Hardness: 6 (Mohs scale); Color: Dark gray to black, often weathering to brown; Luster: Dull to earthy; Texture: Vesicular (contains small cavities/voids), fine-grained (aphanitic); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to black, often weathering to brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to black, often weathering to brown; Luster: Dull to earthy; Texture: Vesicular (contains small cavities/voids), fine-grained (aphanitic); 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. The holes (vesicles) are created by gas bubbles that were trapped in the lava as it solidified.
Uses & applications
Used as aggregate in construction, road base, shoreline protection (riprap), and occasionally as a lightweight abrasive or decorative landscaping stone.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (high density), and characteristic Swiss-cheese-like holes. Found in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.
