igneous
Scoria
Vesicular Basalt / Scoria
Hardness: 5-6 Mohs; Color: Dark red, black, or dark brown; Luster: Dull or earthy; Structure: Highly vesicular/bubbly texture with aphanitic (fine-grained) groundmass; Specific Gravity: Relatively low because of air pockets, though it typically sinks in water.
- Hardness
- 5-6 Mohs
- Color
- Dark red, black, or dark brown
- Luster
- Dull or earthy
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Physical properties
Hardness: 5-6 Mohs; Color: Dark red, black, or dark brown; Luster: Dull or earthy; Structure: Highly vesicular/bubbly texture with aphanitic (fine-grained) groundmass; Specific Gravity: Relatively low because of air pockets, though it typically sinks in water.
Formation & geological history
Formed from volcanic eruptions where gas-rich magma (usually basaltic or andesitic) cools rapidly at the surface, trapping gas bubbles as the rock solidifies. Primarily found in volcanic cones and lava flows.
Uses & applications
Commonly used in landscaping (lava rocks), gas grills, high-temperature insulation, drainage systems, and as a lightweight aggregate in concrete construction.
Geological facts
Scoria is different from pumice because its vesicles (bubbles) are larger and it has thicker cell walls, making it dense enough to sink in water, unlike most pumice specimens.
Field identification & locations
Identify by its dark color and 'sponge-like' appearance with many holes. It is commonly found near volcanic vents and cinder cones such as those in the western United States, Iceland, and Italy.
