igneous
Scoria (with likely iron oxidation)
Scoria (Basaltic Scoria)
Hardness: 5-6 (Mohs). Color: Dark brown, reddish-brown, or black. Luster: Dull to submetallic. Crystal structure: Aphanitic (fine-grained) with high vesicularity (small holes/voids). Specific gravity: 2.0-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark brown, reddish-brown, or black
- Luster
- Dull to submetallic
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Physical properties
Hardness: 5-6 (Mohs). Color: Dark brown, reddish-brown, or black. Luster: Dull to submetallic. Crystal structure: Aphanitic (fine-grained) with high vesicularity (small holes/voids). Specific gravity: 2.0-3.0.
Formation & geological history
Formed from gas-rich basaltic or andesitic magma. As the lava is erupted, dissolved gases expand into bubbles (vesicles) which are frozen into the rock as it quickly solidifies. Common in volcanic cinder cones.
Uses & applications
Used in landscaping (lava rock), gas grills, high-temperature insulation, drainage stones, and lightweight concrete aggregates.
Geological facts
Scoria is often mistaken for pumice; however, scoria has larger vesicles, thicker walls between vesicles, and is dense enough to sink in water, whereas pumice often floats.
Field identification & locations
Identify by its highly vesicular (bubbly) texture and dark color. It feels relatively lightweight for its size but is heavier than pumice. Common in volcanic regions such as the Western US, Iceland, and Italy.
