Scoria (Red Lava Rock)

Physical Properties

Hardness: 5-6 (Mohs scale); Color: Dark red to reddish-brown; Luster: Dull, earthy; Crystal structure: Aphanitic/glassy with vesicular texture; Specific gravity: 0.8 to 2.1 (often sinks in water, unlike pumice); Vesicular (contains many bubble-like holes).

Formation & Geological History

Formed through volcanic eruptions of basaltic or andesitic magma. As gas escapes from cooling lava, it creates a porous, vesicular texture. These are generally from Cenozoic era volcanic activity in environments such as cinder cones.

Uses & Applications

Used extensively in landscaping (lava rock), aquarium filtration, road traction on ice, gas grills, and high-temperature insulation in industrial applications.

Geological Facts

Scoria contains larger voids and thicker cell walls than its volcanic cousin, pumice. While pumice often floats, scoria usually sinks because its density is higher and bubbles are larger and more connected.

Field Identification & Locations

Identify by its highly vesicular (bubbly) texture and red color caused by the oxidation of iron within the basaltic magma. Commonly found near volcanic sites and in landscaping supplies around the world.

Identified on: 4/26/2026

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