Scoria (Red Lava Rock)

Physical Properties

Hardness: 5-6 Mohs; Color: reddish-brown to dark red; Luster: dull/earthy; Crystal Structure: aphanitic/vesicular (glassy with gas bubbles); Specific Gravity: 0.8-2.1 (lightweight but usually sinks in water).

Formation & Geological History

Formed through the rapid cooling of basaltic or andesitic magma. The red color is caused by the oxidation of iron (rusting) during or after the eruption. Found in volcanic cinder cones.

Uses & Applications

Landscaping, gas barbecue grills, high-temperature insulation, drainage rock, and lightweight aggregate in concrete.

Geological Facts

Scoria differs from pumice because it has larger vesicles and thicker cell walls, making it denser. While many think all lava rocks float, scoria usually sinks because its density is higher than water.

Field Identification & Locations

Identify in the field by its distinct vesicular (holey) texture and 'crunchy' feel. Common in volcanic regions like Iceland, Hawaii, and the Western United States. Collectors look for unique shapes.

Identified on: 4/26/2026

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