igneous
Vesicular basalt (scoria-like volcanic rock)
Vesicular basalt; chiefly plagioclase, pyroxene, and olivine
AI-generated identification · may be incorrectDark gray-brown, highly porous, dull to slightly glassy, with abundant gas cavities; hardness about 5–6 Mohs, fine-grained groundmass, and no obvious cleavage. It is denser and generally darker than pumice, though this specimen appears weathered and intermediate in texture.
Identified More igneous →
Explore Vesicular basalt (scoria-like volcanic rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, highly porous, dull to slightly glassy, with abundant gas cavities; hardness about 5–6 Mohs, fine-grained groundmass, and no obvious cleavage. It is denser and generally darker than pumice, though this specimen appears weathered and intermediate in texture.
Formation & geological history
Forms when basaltic lava cools rapidly while trapped gas bubbles create vesicles, commonly in lava flows or volcanic vents. Most examples are geologically young, ranging from recent eruptions to Cenozoic volcanic rocks.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasive, and occasionally in concrete; attractive pieces may be collected but are rarely used in jewelry.
Geological facts
The holes are vesicles, preserved bubbles formed by escaping water vapor and volcanic gases. Iron oxidation can produce the brown weathering color.
Field identification & locations
Common near basaltic volcanoes, including Hawaii, Iceland, the Galápagos, and western North America; identify it by dark color, irregular pores, and relatively high weight compared with pumice. Value is typically $1–$10 for a common hand specimen, or $10–$30 for unusual display pieces.
