igneous
Scoria (Lava Rock)
Scoria / Mafic volcanic rock
Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown or black. Luster: Dull to sub-vitreous. Texture: Highly vesicular (honeycombed with gas bubbles). Specific Gravity: Approximately 0.8-2.1 (lightweight and often floats in water briefly).
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark brown or black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown or black. Luster: Dull to sub-vitreous. Texture: Highly vesicular (honeycombed with gas bubbles). Specific Gravity: Approximately 0.8-2.1 (lightweight and often floats in water briefly).
Formation & geological history
Formed from extrusive volcanic activity where gas-rich basaltic or andesitic magma cools rapidly. The vesicles form as gas bubbles escape during crystallization. Common in Cenozoic volcanic fields.
Uses & applications
Used in landscaping (lava rock mulch), gas grills, high-temperature insulation, drainage systems, and as an abrasive in stone-washed denim production.
Geological facts
Scoria differs from pumice in that it has larger vesicles and thicker cell walls, generally making it heavier and darker due to higher iron and magnesium content.
Field identification & locations
Identify by its 'swiss cheese' appearance, rough texture, and lightweight feel. Commonly found near cinder cones and volcanic shields in places like Iceland, Hawaii, and Arizona.
