igneous
Scoria (Lava Rock)
Scoria
Hardness: 5-6 (variable); Color: Dark brown, black, or reddish; Luster: Dull to submetallic; Structure: Vesicular (highly porous/holed); Cleavage: None; Specific Gravity: 2.0-3.0 (low for a rock due to air pockets).
- Hardness
- 5-6 (variable)
- Color
- Dark brown, black, or reddish
- Luster
- Dull to submetallic
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Physical properties
Hardness: 5-6 (variable); Color: Dark brown, black, or reddish; Luster: Dull to submetallic; Structure: Vesicular (highly porous/holed); Cleavage: None; Specific Gravity: 2.0-3.0 (low for a rock due to air pockets).
Formation & geological history
Formed through volcanic activity where gas is trapped in cooling basaltic or andesitic magma, creating a vesicular texture. It is typical of relatively recent geological ages (Holocene/Pleistocene), appearing near volcanic vents.
Uses & applications
Used in landscaping, high-temperature insulation, gas grills (lava rocks), drainage systems, and as an abrasive in stone-washing textiles.
Geological facts
Scoria is often mistaken for pumice, but it is denser and has larger vesicles with thicker walls. Unlike pumice, scoria is too heavy to float in water.
Field identification & locations
Identify by its dark color and 'sponge-like' appearance with many visible holes. It is commonly found in volcanic fields such as those in Iceland, Hawaii, and the Canary Islands. Collectors search for specimens with unique colors or large vesicles.
