igneous
Vesicular Basalt (Scoria)
Vesicular Basalt
Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) with vesicles (gas bubbles); Specific gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- dark gray, black, or reddish-brown
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) with vesicles (gas bubbles); Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) are created by trapped gas bubbles that escaped as the lava solidified near the surface of a volcano.
Uses & applications
Used in landscaping, high-temperature insulation, drainage rock, gas grill 'lava rocks', and as an abrasive in stone-washing processes.
Geological facts
Scoria is often mistaken for pumice; however, basaltic scoria is denser and will usually sink in water, whereas pumice floats. It is common on the surfaces of shield volcanoes.
Field identification & locations
Identify by its 'Swiss cheese' texture and dark color. Common in volcanic regions like Hawaii, Iceland, and the Pacific Northwest. Look for lightweight (relative to solid rock) vesicular textures.
