Scoria (Lava Rock)

Physical Properties

Vesicular texture (highly porous), hardness: 5-6 (Mohs), color: dark gray to black or reddish-brown, luster: dull/earthy, crystal structure: fine-grained or glassy (aphanitic), specific gravity: 0.8-2.1 (lightweight).

Formation & Geological History

Formed from gas-rich basaltic magma during volcanic eruptions. As lava is ejected, cooling is rapid, and escaping gas bubbles are trapped, creating the holes (vesicles). Primarily Cenozoic in age for most surface deposits.

Uses & Applications

Used extensively in landscaping, gas grills, high-temperature insulation, drainage systems, and as an abrasive in stone-washed denim production.

Geological Facts

Scoria is often confused with pumice, but scoria is denser, has larger vesicles, and usually has a mafic (darker) composition. It sinks in water, whereas many pumice specimens float.

Field Identification & Locations

Identified by its 'Swiss cheese' appearance, rough texture, and lightweight feel relative to size. Commonly found near cinder cones and basaltic volcanic fields (e.g., Iceland, Hawaii, Western USA).

Identified on: 4/28/2026

Mode: Standard