igneous
Scoria (Red Lava Rock)
Scoria (Aphanitic-Vesicular Mafic Rock)
Color: reddish-brown to dark red (due to oxidation); Hardness: 5-6 Mohs; Luster: dull to earthy; Structure: highly vesicular (pitted with gas bubbles); Specific Gravity: low; Texture: glass-like but rough.
- Hardness
- 5-6 Mohs
- Color
- reddish-brown to dark red (due to oxidation)
- Luster
- dull to earthy
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Physical properties
Color: reddish-brown to dark red (due to oxidation); Hardness: 5-6 Mohs; Luster: dull to earthy; Structure: highly vesicular (pitted with gas bubbles); Specific Gravity: low; Texture: glass-like but rough.
Formation & geological history
Formed from the rapid cooling of basaltic or andesitic lava containing high gas content. The 'vesicles' or holes are formed as gas bubbles are trapped during solidification. Usually found in volcanic cinder cones.
Uses & applications
Landscaping (decorative mulch), gas grill heat stones, lightweight concrete aggregate, abrasive stone (pumice-like uses), and aquarium bio-filtration.
Geological facts
Scoria is heavier and denser than pumice and generally sinks in water, whereas pumice floats. Its red color is indicative of iron oxidation occurring during or after the eruption.
Field identification & locations
Identify by its light weight (though heavier than pumice) and high density of bubble-like cavities. Common near young volcanic regions like the American Southwest, Iceland, and Hawaii.
