igneous
Likely tumbled basalt or vesicular volcanic rock
Basalt, possibly amygdaloidal basalt
AI-generated identification · may be incorrectDark gray-brown, smoothly tumbled, with many rounded pale cavities or mineral-filled vesicles; typically dull to slightly vitreous luster, hardness about 5–6, fine-grained, and without visible cleavage. Exact identification is limited by the small, low-resolution image.
Identified More igneous →
Explore Likely tumbled basalt or vesicular volcanic rock in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, smoothly tumbled, with many rounded pale cavities or mineral-filled vesicles; typically dull to slightly vitreous luster, hardness about 5–6, fine-grained, and without visible cleavage. Exact identification is limited by the small, low-resolution image.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near Earth’s surface; vesicles formed from trapped gas and may later fill with minerals. Basalt ranges from Precambrian to modern age and is common in volcanic regions.
Uses & applications
Used extensively as crushed aggregate, road stone, building stone, and occasionally as a decorative or lapidary material. Common tumbled pieces have modest collector value.
Geological facts
The circular spots may be vesicles, zeolite, calcite, or weathered inclusions rather than true holes. A streak, hardness, and close inspection of a fresh surface would improve identification.
Field identification & locations
Common worldwide in volcanic terrains, including Hawaii, Iceland, India, the western United States, and oceanic crust. It is distinguished from sandstone or concrete by its dense volcanic texture, irregular vesicles, and lack of cemented grains.
