igneous
Scoria
Scoria (Vesicular Basalt)
Hardness: 5-6 Mohs. Color: usually dark brown, black, or red. Luster: Dull/Sub-glassy. Structure: Highly vesicular (honeycombed with gas bubbles). Cleavage: None. Specific gravity: low (often sinks in water, unlike pumice).
- Hardness
- 5-6 Mohs
- Color
- usually dark brown, black, or red
- Luster
- Dull/Sub-glassy
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Physical properties
Hardness: 5-6 Mohs. Color: usually dark brown, black, or red. Luster: Dull/Sub-glassy. Structure: Highly vesicular (honeycombed with gas bubbles). Cleavage: None. Specific gravity: low (often sinks in water, unlike pumice).
Formation & geological history
Formed from the cooling of mafic magma (basaltic or andesitic) that is rich in dissolved gases. As the magma erupts, gases expand creating vesicles that are frozen into the rock as it solidifies.
Uses & applications
Used in landscaping as 'lava rock', high-temperature insulation, lightweight concrete aggregate, oil well drilling, and as a drainage medium in horticulture.
Geological facts
Scoria is often confused with pumice, but pumice is felsic (lighter color and weight), whereas scoria is mafic (darker and denser). Large deposits are commonly found near volcanic cinder cones.
Field identification & locations
Identify by its dark color, rough/sharp texture, and numerous distinctive holes (vesicles). Found globally in volcanic regions like Iceland, Hawaii, and Italy.
