igneous
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Hardness: 5-6 Mohs scale; Color: Dark red, brown, black, or dark grey; Luster: Dull/Earthy; Structure: Vesicular (highly porous/pitted); Specific gravity: 2.0-3.0 (dense enough to sink in water, unlike pumice).
- Hardness
- 5-6 Mohs scale
- Color
- Dark red, brown, black, or dark grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs scale; Color: Dark red, brown, black, or dark grey; Luster: Dull/Earthy; Structure: Vesicular (highly porous/pitted); Specific gravity: 2.0-3.0 (dense enough to sink in water, unlike pumice).
Formation & geological history
Formed from extrusive volcanic eruptions where gas bubbles are trapped as the lava cools rapidly. It is typically mafic/basaltic in composition. Found in volcanic regions ranging from prehistoric eras to modern eruptions.
Uses & applications
Used extensively in landscaping, gas grills, high-temperature insulation, drainage systems, and as an abrasive in concrete or road construction.
Geological facts
Scoria is often confused with pumice, but it is much heavier and darker because it contains more iron and magnesium. Its holes - called vesicles - are the result of volcanic gasses expanding as the lava reached the surface.
Field identification & locations
Identify by its 'swiss cheese' appearance, rough texture, and dark color. It feels lightweight for its size but will not float in water. Commonly found near cinder cones and volcanic fields in places like the American Southwest, Iceland, and Hawaii.
