igneous
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Hardness: 5-6 Mohs; Color: Dark brown, black, or reddish; Luster: Dull/Glassy; Crystal structure: Aphanitic (fine-grained) with high vesicularity; Specific gravity: Low (often floats on water briefly but usually sinks)
- Hardness
- 5-6 Mohs
- Color
- Dark brown, black, or reddish
- Luster
- Dull/Glassy
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Physical properties
Hardness: 5-6 Mohs; Color: Dark brown, black, or reddish; Luster: Dull/Glassy; Crystal structure: Aphanitic (fine-grained) with high vesicularity; Specific gravity: Low (often floats on water briefly but usually sinks)
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic or andesitic magma during volcanic eruptions. The holes (vesicles) are created by trapped gas bubbles that expand as pressure drops.
Uses & applications
Used in landscaping for ground cover, as a drainage material in construction, for gas grill heat rocks, and as a lightweight aggregate in concrete.
Geological facts
Scoria differs from pumice in that it has larger vesicles and thicker cell walls, making it denser and darker. Some cultures have used it as a grinding stone or thermal insulator for centuries.
Field identification & locations
Identify by its 'Swiss cheese' like holes, rough texture, and lightweight feel. Commonly found in volcanic fields, cinder cones, and near basaltic lava flows in regions like Iceland, Hawaii, or the American Southwest.
