igneous
Red Scoria (Lava Rock)
Scoria (Vesicular Basalt)
Hardness: 5-6 Mohs. Color: Deep reddish-brown to dark maroon. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with air bubbles), glass-like fine crystalline matrix. Specific Gravity: Variable but often low enough to be relatively lightweight.
- Hardness
- 5-6 Mohs
- Color
- Deep reddish-brown to dark maroon
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Deep reddish-brown to dark maroon. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with air bubbles), glass-like fine crystalline matrix. Specific Gravity: Variable but often low enough to be relatively lightweight.
Formation & geological history
Formed from the rapid cooling of basaltic or andesitic magma containing high amounts of dissolved gas. As the magma erupts, gases expand and escape, leaving behind a 'frothy' stone. Found in volcanic cinder cones globally.
Uses & applications
Commonly used in landscaping (mulch replacement), gas grills for heat retention, drainage systems, high-temperature insulation, and lightweight concrete aggregate.
Geological facts
Unlike pumice, which is similar but lighter in color and more buoyant, scoria sinks in water because its vesicle walls are thicker and the rock has a more mafic (iron-rich) chemical composition.
Field identification & locations
Identify in the field by its distinctive 'honeycomb' texture, rough surface, and reddish color caused by the oxidation of iron during eruption. It is ubiquitous in volcanic regions like the American Southwest, Iceland, and Italy.
