igneous
Red Scoria (Lava Rock)
Vesicular Basalt / Scoria
Hardness: 5-6 (Mohs scale); Color: Deep reddish-brown to dark gray; Luster: Dull to earthy; Structure: Vesicular (full of small holes or bubbles); Cleavage: None; Specific Gravity: Relatively low/light due to air pockets.
- Hardness
- 5-6 (Mohs scale)
- Color
- Deep reddish-brown to dark gray
- Luster
- Dull to earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Deep reddish-brown to dark gray; Luster: Dull to earthy; Structure: Vesicular (full of small holes or bubbles); Cleavage: None; Specific Gravity: Relatively low/light due to air pockets.
Formation & geological history
Formed from gas-rich basaltic magma that ejected from a volcano during an explosive eruption. The holes (vesicles) are created by trapped gas bubbles that freeze in place as the lava cools rapidly. Typically found in Cenozoic volcanic fields.
Uses & applications
Commonly used in landscaping (decorative rock), ground cover for fire pits, high-temperature insulation, and as a lightweight aggregate in concrete or drainage systems.
Geological facts
Scoria is different from pumice because it has thicker cell walls and is denser; unlike pumice, most scoria will sink in water. The red color is caused by the oxidation of iron within the lava while it is still hot.
Field identification & locations
Identify by its 'sponge-like' appearance, rough/sharp texture, and reddish hue. Common in regions with past volcanic activity like Arizona, Iceland, Italy, and Hawaii. Collectors look for pieces with distinct, uniform vesicles or embedded crystals.
