Vesicular Basalt

Physical Properties

Hardness: 6 (Mohs scale), Color: Dark grey to black or dark brown, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), includes vesicles (gas bubbles), Cleavage: None

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. The holes (vesicles) are created by trapped gas bubbles that escaped as the rock solidified.

Uses & Applications

Used in construction as aggregate, road base, and decorative landscaping stones. Higher porosity varieties like scoria are used for gas grills and heat insulation.

Geological Facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Vesicular basalt is common in volcanic fields like those found in Hawaii or Iceland.

Field Identification & Locations

Identify in the field by its dark color, heavy weight (high specific gravity), and the presence of small pits or holes on the surface. Commonly found near volcanic sites or in riverbeds downstream from volcanic ranges.

Identified on: 4/30/2026

Mode: Standard