igneous
Scoria
Vesicular Basalt / Scoria
Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: Low (often floats briefly on water due to vesicles).
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark reddish-brown to black
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: Low (often floats briefly on water due to vesicles).
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic lava during volcanic eruptions. The holes (vesicles) are created by trapped gas bubbles that expand as pressure drops during the eruption.
Uses & applications
Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, concrete aggregate, and as a drainage material in horticulture.
Geological facts
Scoria differs from pumice in that it has larger vesicles and thicker cell walls, making it denser and darker. Massive deposits are often found in cinder cones around volcanic vents.
Field identification & locations
Identify by its 'Swiss cheese' appearance, lightweight nature, and rough, abrasive texture. Commonly found in volcanic regions like the American Southwest, Iceland, and Italy.
