Vesicular Basalt (Lava Rock)

Physical Properties

Hardness: 5-6 (Mohs), Color: Grey, black, or reddish-brown, Luster: Dull/Earthy, Structure: Fine-grained/Aphanitic with holes (vesicles), Cleavage: None

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The holes were created by gas bubbles being trapped as the lava solidified.

Uses & Applications

Used frequently in landscaping, gas grills, drainage systems, and as an abrasive in stone-washing textiles.

Geological Facts

The 'vesicles' are actually frozen bubbles of volcanic gas. Vesicular basalt makes up a large portion of the oceanic crust and is found in major volcanic fields like Hawaii and Iceland.

Field Identification & Locations

Identify by its lightweight feel relative to size and the presence of numerous small pits or voids. It is commonly found in volcanic regions or along coastlines with volcanic history.

Identified on: 4/30/2026

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