Vesicular Basalt (Pumice-like)

Physical Properties

Hardness: 5-6 (Mohs); Color: Dark grey to brown/tan; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained) with vesicles (voids); Cleavage: None; Specific gravity: 2.8-3.0.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) are created by gas bubbles trapped in the cooling magma. Found in volcanic regions worldwide, typical of Cenozoic to recent eras.

Uses & Applications

Used in landscaping, construction (lightweight aggregate), BBQ grills, and as abrasive stones (pumice style) for skin exfoliation.

Geological Facts

This rock is a piece of the Earth's crust; basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor.

Field Identification & Locations

Identify by its 'holey' or porous texture and relatively heavy weight compared to true pumice. Commonly found in volcanic fields like those in the Pacific Northwest, Hawaii, or Iceland.

Identified on: 4/29/2026

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