igneous
Vesicular Basalt (Scoria)
Aphanitic Mafic Igneous Rock (Vesicular Basalt)
Hardness: 5-6 (Mohs), Color: Dark brown to reddish-brown, Luster: Dull to earthy, Structure: Vesicular (full of small bubbles), Texture: Rough and porous.
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Physical properties
Hardness: 5-6 (Mohs), Color: Dark brown to reddish-brown, Luster: Dull to earthy, Structure: Vesicular (full of small bubbles), Texture: Rough and porous.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava that contains trapped gas bubbles. As the lava cools at the surface, the gas escapes, leaving behind the 'vesicles' or holes.
Uses & applications
Commonly used in landscaping as decorative 'lava rock', in high-temperature insulation, as an abrasive in stone-washing jeans, and for drainage in horticulture.
Geological facts
The holes in this rock are actually frozen snapshots of volcanic gas bubbles. If the holes are very numerous and the rock is light enough to float, it would be classified as pumice (usually from lighter rhyolitic lava).
Field identification & locations
Identify by its lightweight feel compared to solid rocks, its reddish-brown oxidized color, and the presence of numerous small pits or voids. Common in volcanic regions like Hawaii or the Pacific Northwest.
