igneous
Vesicular Basalt (Lava Rock)
Vesicular Basalt (comprising plagioclase feldspar and pyroxene group minerals)
Hardness: 5-6 (Mohs scale); Color: Dark gray to black; Luster: Dull/glassy in small vesicles; Structure: Aphanitic (fine-grained) with many holes (vesicles); Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull/glassy in small vesicles
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark gray to black; Luster: Dull/glassy in small vesicles; Structure: Aphanitic (fine-grained) with many holes (vesicles); Specific Gravity: 2.8-3.0
Formation & geological history
Formed through the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The holes were created by trapped gas bubbles (volatiles) escaping the lava during solidification.
Uses & applications
Commonly used in landscaping as decorative rock, gas grill briquettes, drainage material, and in road construction as aggregate.
Geological facts
Basalt is the most common rock type in the Earth's crust and covers most of the ocean floor. Extensive flows can form unique structures like giant basalt columns.
Field identification & locations
Identify by its dark color, heavy weight compared to pumice, and characteristic holes. Often found in volcanic regions, such as the Pacific Northwest, Hawaii, and Iceland.
