igneous
Scoria
Mafic to intermediate volcanic rock
Hardness: 5-6 on the Mohs scale; Color: Dark brown, black, reddish-brown; Luster: Dull; Crystal structure: Aphanitic with abundant vesicular texture (gas bubbles); Specific gravity: Often less than 1.0 (can float in water if sealed, though denser varieties sink).
- Hardness
- 5-6 on the Mohs scale
- Color
- Dark brown, black, reddish-brown
- Luster
- Dull
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Physical properties
Hardness: 5-6 on the Mohs scale; Color: Dark brown, black, reddish-brown; Luster: Dull; Crystal structure: Aphanitic with abundant vesicular texture (gas bubbles); Specific gravity: Often less than 1.0 (can float in water if sealed, though denser varieties sink).
Formation & geological history
Formed through explosive volcanic eruptions when gas-rich, frothy lava cools rapidly in the air, trapping gas bubbles (vesicles) within the rock matrix.
Uses & applications
Used in landscaping, gas barbecue grills, lightweight aggregate in concrete, drainage works, and as a body exfoliant.
Geological facts
Scoria is commonly referred to as 'lava rock.' Unlike pumice (which is felsic and consistently floats), scoria has larger vesicles, thicker walls, and typically sinks in water.
Field identification & locations
Easily identified by its dark color, rough texture, and distinctive vesicular 'Swiss cheese' appearance. Found worldwide near volcanic regions and cinder cones.
