igneous
Scoria (Lava Rock)
Aphanitic vesicular mafic igneous rock
Hardness: 5-6 Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthly; Structure: Vesicular (full of holes); Cleavage: None/Conchoidal; Specific Gravity: 0.8-2.1 (low due to air pockets)
- Hardness
- 5-6 Mohs scale
- Color
- Reddish-brown to dark brown
- Luster
- Dull/Earthly
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Physical properties
Hardness: 5-6 Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthly; Structure: Vesicular (full of holes); Cleavage: None/Conchoidal; Specific Gravity: 0.8-2.1 (low due to air pockets)
Formation & geological history
Formed through the rapid cooling of gas-rich basaltic or andesitic lava ejected from a volcano. The holes (vesicles) are created by expanding gas bubbles trapped during solidifcation. Found in cinder cones and volcanic fields.
Uses & applications
Used in landscaping for drainage and decoration, gas grills (lava rocks), lightweight concrete production, road surfacing, and high-temperature insulation.
Geological facts
Scoria is similar to pumice, but it is denser and has larger vesicles with thicker walls. Unlike some pumice, most scoria specimens will sink in water because they have a higher specific gravity and iron content.
Field identification & locations
Identify by its 'sponge-like' appearance, rough texture, and lightweight feel. It is commonly found in regions of recent volcanic activity like Arizona, Hawaii, Iceland, and Italy. Look for its characteristic red or black color and sharp edges.
