igneous
Vesicular Basalt / Scoria
Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)
Hardness: 5-6 Mohs; Color: Grey, brown, or reddish-brown; Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Grey, brown, or reddish-brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs; Color: Grey, brown, or reddish-brown; Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) are created by gas bubbles that were trapped in the lava as it solidified. Found in volcanic regions of various geological ages.
Uses & applications
Used in landscaping, heat-resistant gas grill stones, high-temperature insulation, and as an abrasive in 'stone-washed' denim production. Smaller pieces are often used in drainage systems.
Geological facts
This rock is essentially frozen volcanic froth. Because it forms on the surface of lava flows, it often contains higher gas content than the denser basalt found deeper in the flow.
Field identification & locations
Identify by its lightweight feel compared to solid rock and the presence of numerous small to medium cavities. It is commonly found near volcanic vents and rift valleys. Collectors look for unique shapes and iron-oxide staining.
