igneous
Scoria (Lava Rock)
Scoria
Hardness: 5-6 (Mohs); Color: Dark reddish-brown to black; Luster: Dull, earthy; Structure: Vesicular (highly porous/holed); Specific Gravity: 0.8-2.1 (lightweight and often sinks in water unlike pumice).
- Hardness
- 5-6 (Mohs)
- Color
- Dark reddish-brown to black
- Luster
- Dull, earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark reddish-brown to black; Luster: Dull, earthy; Structure: Vesicular (highly porous/holed); Specific Gravity: 0.8-2.1 (lightweight and often sinks in water unlike pumice).
Formation & geological history
Formed from basaltic or andesitic magma. As gas escapes during a volcanic eruption, the cooling lava solidifies with trapped bubbles, creating a porous texture. Typically found in volcanic vents and cinder cones.
Uses & applications
Commonly used in landscaping (lava rock), gas grills for heat retention, drainage in horticulture, high-temperature insulation, and as a lightweight aggregate in concrete.
Geological facts
Scoria is often mistaken for pumice; however, scoria has larger vesicles and thicker walls, making it dense enough to sink in water, whereas pumice generally floats.
Field identification & locations
Identify by its reddish-brown color, lightweight feel (though heavier than pumice), and numerous small holes. Commonly found in volcanic regions such as Arizona, Hawaii, and Iceland.
