igneous
Vesicular Basalt
Mafic Igneous Rock (primarily Plagioclase and Pyroxene)
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathered to rusty brown. Luster: Dull/earthy until wet. Structure: Vesicular (contains air bubbles or gas pits). Density: High.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black, often weathered to rusty brown
- Luster
- Dull/earthy until wet
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Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathered to rusty brown. Luster: Dull/earthy until wet. Structure: Vesicular (contains air bubbles or gas pits). Density: High.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the Earth's surface. The holes (vesicles) were formed by gas bubbles trapped in the cooling lava. Most basalt is relatively young geologically (Cenozoic era).
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, and railroad ballast. Decorative uses include landscaping rocks and aquarium decor.
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
Look for a heavy, dark rock with numerous small pits or holes. Often found in volcanic regions or areas with ancient lava flows. It will not react with acid, unlike limestone.
