Igneous
Scoria (Red Lava Rock)
Scoria (Extrusive Igneous Rock)
Hardness: 5-6 (Mohs scale); Color: Dark red to reddish-brown (oxidized iron); Luster: Dull to sub-vitreous; Structure: Highly vesicular (pitted/bubbly); Specific Gravity: 0.8-2.1 (lightweight/often floats)
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark red to reddish-brown (oxidized iron)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark red to reddish-brown (oxidized iron); Luster: Dull to sub-vitreous; Structure: Highly vesicular (pitted/bubbly); Specific Gravity: 0.8-2.1 (lightweight/often floats)
Formation & geological history
Formed from the rapid cooling and depressurization of gas-rich basaltic or andesitic magma ejected from a volcano. The holes (vesicles) are created by trapped gas bubbles that expand during eruption.
Uses & applications
Used extensively in landscaping, gas grill lava rocks, lightweight concrete aggregate, high-temperature insulation, and aquarium decor.
Geological facts
Scoria is often confused with pumice, but it has thicker cell walls and is denser; while some scoria floats, most eventually sinks. The red color is caused by the oxidation of iron within the magma during eruption.
Field identification & locations
Identify by its 'sponge-like' appearance, rough/abrasive texture, and light weight. Commonly found near cinder cones and volcanic vents in regions like Arizona, Iceland, and Italy.
