igneous
Scoria (Lava Rock)
Scoria (Mafic volcanic rock)
Hardness: 5-6 (Mohs scale); Color: Dark red, brown, or black; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: 2.0-3.0 (lightweight but usually sinks in water).
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark red, brown, or black
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark red, brown, or black; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: 2.0-3.0 (lightweight but usually sinks in water).
Formation & geological history
Formed from basaltic or andesitic magma. As gas escapes during an explosive volcanic eruption, the molten rock cools quickly, trapping bubbles of gas (vesicles). It is often found in volcanic cinder cones and lava flows.
Uses & applications
Commonly used in landscaping (drainage and decoration), gas grills (lava rocks), high-temperature insulation, and as a lightweight aggregate in concrete and road construction.
Geological facts
Scoria is different from pumice because it has larger vesicles and thicker cell walls, making it denser. While pumice usually floats, most scoria will sink. Red scoria is often used as 'lava rock' for decorative gardens.
Field identification & locations
Identify by its 'Swiss cheese' appearance, rough/sharp edges, and reddish-brown to black color. It is extremely common in volcanic regions like the American Southwest, Iceland, and Italy.
