igneous
Vesicular Basalt
Aphanitic Mafic Igneous Rock (with vesicles)
Hardness: 5-6 (Mohs scale), Color: Dark grey to black or brownish, Luster: Dull/Earthy, Texture: Vesicular (containing numerous small cavities or bubbles), Specific Gravity: 2.8-3.0
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark grey to black or brownish, Luster: Dull/Earthy, Texture: Vesicular (containing numerous small cavities or bubbles), Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The holes (vesicles) are created by gas bubbles trapped in the lava as it solidifies. Common in volcanic regions worldwide.
Uses & applications
Used in construction for road base, concrete aggregate, and railroad ballast. Highly porous varieties are used in landscaping (lava rocks) and as abrasive cleaners (pumice-like basalt).
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Large-scale basalt flows can create massive plateaus like the Columbia River Plateau.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and characteristic holes or gas bubbles. It is frequently found in volcanic fields or near ancient lava flows.
