igneous
Vesicular Basalt (Scoria)
Aphanitic Mafic Igneous Rock with Vesicular Texture
Hardness: 5-6 Mohs. Color: Reddish-brown to dark grey. Luster: Dull/Earthy. Texture: Vesicular (full of small cavities). Crystal structure: Microcrystalline or glassy. Specific Gravity: 2.5-3.0.
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark grey. Luster: Dull/Earthy. Texture: Vesicular (full of small cavities). Crystal structure: Microcrystalline or glassy. Specific Gravity: 2.5-3.0.
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic lava erupted from volcanoes. The holes (vesicles) are created by gas bubbles that were trapped as the lava solidified. They are typically found in recent volcanic fields or cinder cones.
Uses & applications
Used in landscaping, high-temperature insulation, gas grill lava rocks, drainage systems, and as an abrasive in stone-washing processes. Common in road construction as lightweight aggregate.
Geological facts
Scoria is often mistaken for pumice; however, scoria is denser, has thicker vesicle walls, and sinks in water, whereas pumice floats. The reddish color is usually due to the oxidation of iron within the lava.
Field identification & locations
Identify in the field by its porous, 'holier-than-thou' appearance, lightweight feel compared to solid basalt, and sharp, abrasive surface. Commonly found in volcanic regions like Hawaii, Iceland, and the American Southwest.
