igneous
Vesicular basalt (scoria-like volcanic rock)
Vesicular basalt, primarily plagioclase feldspar, pyroxene, and olivine
AI-generated identification · may be incorrectTypically dark gray to black, fine-grained, and highly vesicular with many rounded gas cavities; hardness about 5–6 Mohs, dull to slightly glassy luster, and specific gravity commonly 2.4–2.9. The specimen appears weathered and unusually pale, possibly from surface alteration or mineral infilling.
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
Typically dark gray to black, fine-grained, and highly vesicular with many rounded gas cavities; hardness about 5–6 Mohs, dull to slightly glassy luster, and specific gravity commonly 2.4–2.9. The specimen appears weathered and unusually pale, possibly from surface alteration or mineral infilling.
Formation & geological history
Forms when basaltic lava cools rapidly at or near the surface, trapping expanding gas bubbles; most examples are Cenozoic or younger, though basalt occurs throughout Earth’s geologic history. Commonly associated with lava flows, cinders, and volcanic cones.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and occasionally decorative material; generally has little jewelry value.
Geological facts
Its holes are vesicles, not fossils; mineral-rich groundwater may later line or fill them with zeolites, calcite, or quartz.
Field identification & locations
Identify by low density, irregular vesicles, fine texture, and lack of sedimentary layering; common worldwide in volcanic regions such as Hawaii, Iceland, Italy, and the western United States.
