Scoria (Red Lava Rock)

Physical Properties

Hardness: 5-6 (Mohs scale); Color: Reddish-brown to dark red; Luster: Dull/Earthy; Structure: Vesicular (highly porous/pitted); Texture: Pyroclastic; Specific Gravity: Relatively low (some float briefly, but most sink unlike Pumice).

Formation & Geological History

Formed from extrusive volcanic eruptions of mafic magma (basaltic or andesitic). As lava cools rapidly on the surface, trapped gas bubbles (vesicles) expand and create the porous texture. Common in Cenozoic volcanic fields.

Uses & Applications

Landscaping and garden decoration, gas grill heat rocks, lightweight concrete aggregate, high-temperature insulation, and road traction in snowy conditions.

Geological Facts

Red scoria gets its distinct color from the oxidation of iron within the lava as it erupts and cools. While it looks like pumice, scoria is denser and usually has larger vesicles with thicker walls.

Field Identification & Locations

Identify by its 'sponge-like' appearance, lightweight feel, and sharp, abrasive edges. Commonly found in volcanic regions like Iceland, Hawaii, the Canary Islands, and the Western United States.

Identified on: 4/26/2026

Mode: Standard