igneous
Vesicular Basalt (or Rhyolite)
Extrusive Igneous Rock with Vesicular Texture
Hardness: 5-7 (Mohs scale), Color: light grey to tan (weathered), Luster: dull/earthy, Crystal structure: Aphanitic (fine-grained), Cleavage: none, notable for small cavities (vesicles) caused by gas bubbles.
Identified More igneous →
Explore Vesicular Basalt (or Rhyolite) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 (Mohs scale), Color: light grey to tan (weathered), Luster: dull/earthy, Crystal structure: Aphanitic (fine-grained), Cleavage: none, notable for small cavities (vesicles) caused by gas bubbles.
Formation & geological history
Formed through the rapid cooling of lava on or near the Earth's surface. The pits or 'vesicles' are formed by gas bubbles trapped in the cooling magma as pressure is released during a volcanic eruption.
Uses & applications
Used in landscaping, construction (as aggregate), thermal insulation, and sometimes in cosmetics/skin care as pumice-like scrub stones if sufficiently porous.
Geological facts
Vesicular rocks like this are essentially fossilized foam from a volcanic eruption. If the vesicles are extremely dense, the rock may float (pumice).
Field identification & locations
Identify by looking for 'swiss cheese' holes in a hard, stony matrix. Often found in volcanic regions, riverbeds downstream from volcanic sites, or as imported landscaping gravel.
