igneous
Scoria (Red Lava Rock)
Scoria (Vesicular Basalt/Andesite)
Hardness: 5-6 (Mohs scale); Color: Reddish-brown to dark red (due to oxidation); Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: Low (often floats in water temporarily until saturated).
- Hardness
- 5-6 (Mohs scale)
- Color
- Reddish-brown to dark red (due to oxidation)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Reddish-brown to dark red (due to oxidation); Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: Low (often floats in water temporarily until saturated).
Formation & geological history
Formed from the rapid cooling of gas-rich, mafic or intermediate lava. The 'holes' are vesicles formed by trapped gas bubbles. Red coloring occurs when iron-rich minerals oxidize during or after eruption. Typically Holocene to Pleistocene in age.
Uses & applications
Used extensively in landscaping, drainage systems, gas grills (lava rocks), lightweight concrete aggregate, and high-temperature insulation.
Geological facts
Scoria differs from pumice because it has thicker cell walls and is denser; while pumice is felsic and light-colored, scoria is mafic and dark or red. Many 'lava rocks' in backyard grills are actually mined scoria.
Field identification & locations
Identify by its 'Swiss cheese' texture, rough/sharp surface, and very light weight. It is commonly found in volcanic fields like those in Iceland, Italy, the Canary Islands, and the Western United States (Arizona, New Mexico).
