igneous
Scoria (Vesicular Basalt)
Scoria (Vesicular Igneous Rock)
Hardness: 5-6 (Mohs). Color: dark reddish-brown, black, or dark gray. Luster: dull to sub-metallic. Texture: highly vesicular (pitted with gas bubbles), fine-grained (aphanitic), jagged edges. Specific Gravity: relatively low due to porosity.
- Hardness
- 5-6 (Mohs)
- Color
- dark reddish-brown, black, or dark gray
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 5-6 (Mohs). Color: dark reddish-brown, black, or dark gray. Luster: dull to sub-metallic. Texture: highly vesicular (pitted with gas bubbles), fine-grained (aphanitic), jagged edges. Specific Gravity: relatively low due to porosity.
Formation & geological history
Formed through the rapid cooling of basaltic or andesitic lava containing high amounts of dissolved gases. As the lava erupts, the pressure drops and gases expand to create vesicles (holes) before the rock solidifies. Found in volcanic regions of all ages.
Uses & applications
Commonly used in landscaping as decorative 'lava rock,' in gas grills to distribute heat, as high-temperature insulation, and as an aggregate in lightweight concrete for construction.
Geological facts
Scoria is often confused with pumice, but scoria is denser, has larger bubbles, and generally sinks in water, whereas pumice is light enough to float. It frequently forms the bulk of cinder cone volcanoes.
Field identification & locations
Identify in the field by its sponge-like appearance, lightweight feel compared to solid rock, and sharp, abrasive surface. Found near volcanic vents and cinder cones globally, particularly in Iceland, the Canary Islands, and the Western USA.
