Igneous
Scoria (Red Lava Rock)
Scoria (Vesicular basaltic rock)
Hardness: 5-6 Mohs. Color: Reddish-brown to dark maroon (due to iron oxidation). Luster: Dull to sub-vitreous. Texture: Highly vesicular (pitted with gas bubbles). Specific Gravity: Approximately 0.8 to 2.1 (often lightweight). Structure: Aphanitic (fine-grained) with large vesicles.
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark maroon (due to iron oxidation)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark maroon (due to iron oxidation). Luster: Dull to sub-vitreous. Texture: Highly vesicular (pitted with gas bubbles). Specific Gravity: Approximately 0.8 to 2.1 (often lightweight). Structure: Aphanitic (fine-grained) with large vesicles.
Formation & geological history
Formed through the rapid cooling of basaltic or andesitic lava containing high gas content. As the lava erupts, trapped gases expand to form bubbles, which are then 'frozen' in place as the rock solidifies. These often date from the Cenozoic era to recent volcanic activity.
Uses & applications
Commonly used in landscaping (decorative 'lava rock'), gas grills (heat retention), lightweight aggregate in concrete, road base construction, and high-temperature insulation.
Geological facts
Scoria is different from pumice in that it contains larger vesicles, has thicker cell walls, and is denser, meaning it usually sinks in water whereas pumice floats. The reddish color is usually the result of iron within the lava rusting (oxidizing) as it meets the air.
Field identification & locations
Identify in the field by its distinct 'Swiss cheese' appearance, rough/abrasive texture, and reddish-brown color. Found globally in volcanic regions like Iceland, Hawaii, the Canary Islands, and the Cinder Cone Natural Area in California.
