Vesicular Basalt

Physical Properties

Hardness: 5-6 (Mohs scale); Color: Dark grey to black; Luster: Dull to submetallic; Crystal Structure: Aphanitic (fine-grained matrix); Cleavage: None (subconchoidal fracture); Specific Gravity: 2.8-3.0.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic) at or near the Earth's surface. The holes (vesicles) are created by gas bubbles that were trapped in the lava as it solidified.

Uses & Applications

Commonly used as an aggregate in construction (roads/railroads), as dimensional stone for veneers or pavers, and as decorative rock in landscaping or aquariums.

Geological Facts

Basalt is the most common rock in 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 (relative to size), and the presence of small pits or vesicles. It is commonly found in volcanic regions, such as Hawaii, Iceland, or the Pacific Northwest.

Identified on: 5/15/2026

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