igneous
Red vesicular basalt (tumbled volcanic rock)
Vesicular basalt; predominantly plagioclase, pyroxene, and iron-rich olivine
AI-generated identification · may be incorrectDark reddish-brown, fine-grained, dull to slightly earthy luster, with abundant small gas vesicles and rounded edges from tumbling. Hardness is approximately 5.5–6.5 Mohs; crystals are mostly microscopic, with no obvious cleavage.
Identified More igneous →
Explore Red vesicular basalt (tumbled volcanic rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark reddish-brown, fine-grained, dull to slightly earthy luster, with abundant small gas vesicles and rounded edges from tumbling. Hardness is approximately 5.5–6.5 Mohs; crystals are mostly microscopic, with no obvious cleavage.
Formation & geological history
Formed when fluid basaltic lava cooled rapidly at or near Earth’s surface, trapping gas bubbles; the red color commonly reflects oxidation of iron-bearing minerals. Basalt ranges from recent eruptions to specimens millions or billions of years old; this sample’s age cannot be determined visually.
Uses & applications
Used as landscaping stone, aggregate, road material, and occasionally in decorative rock collections or polished-stone products; it has little gemstone value.
Geological facts
Vesicles distinguish it from dense basalt, while its reddish coloration is often called oxidized or weathered basalt. It may superficially resemble scoria, but scoria is generally much more highly vesicular and lightweight.
Field identification & locations
Common worldwide in volcanic regions, including Hawaii, Iceland, the western United States, India, and oceanic crust. Confirm with a dark streak, lack of acid reaction, moderate density, and magnetic response if iron-rich; a hand lens may reveal tiny feldspar crystals.
