igneous
Red Scoria
Scoria (Vesicular Basalt/Andesite)
Hardness: 5-6 (Mohs); Color: dark reddish-brown to black; Luster: dull/earthy; Structure: highly vesicular (pitted with gas bubbles); Specific gravity: low (often floats initially until waterlogged)
- Hardness
- 5-6 (Mohs)
- Color
- dark reddish-brown to black
- Luster
- dull/earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: dark reddish-brown to black; Luster: dull/earthy; Structure: highly vesicular (pitted with gas bubbles); Specific gravity: low (often floats initially until waterlogged)
Formation & geological history
Formed from gas-rich mafic magma (basaltic or andesitic) cooling rapidly during explosive volcanic eruptions. The holes (vesicles) are created by trapped gas during solidification.
Uses & applications
Used extensively in landscaping, gas grill lava rocks, drainage systems, high-temperature insulation, and as a lightweight aggregate in concrete.
Geological facts
Scoria is technically a glass, but is classified as an extrusive igneous rock. Unlike pumice, which is felsic and very light, scoria is mafic and usually sinks in water due to thicker cell walls.
Field identification & locations
Identify in the field by its distinct 'sponge-like' appearance and sharp, jagged edges. Commonly found on the flanks of cinder cone volcanoes.
