igneous
Vesicular basalt (lava rock)
Vesicular basalt, composed mainly of plagioclase, pyroxene, and often olivine
AI-generated identification · may be incorrectDark gray, fine-grained, and dotted with gas-bubble cavities (vesicles); typically Mohs 5–6, with a dull to slightly waxy luster and no obvious cleavage. The cavities distinguish it from many other dark volcanic rocks.
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Physical properties
Dark gray, fine-grained, and dotted with gas-bubble cavities (vesicles); typically Mohs 5–6, with a dull to slightly waxy luster and no obvious cleavage. The cavities distinguish it from many other dark volcanic rocks.
Formation & geological history
Forms when basaltic lava cools at or near the surface and trapped gas leaves bubbles. Its age cannot be determined from the image; vesicular basalt occurs in volcanic regions of many ages.
Uses & applications
Used as decorative stone, landscaping material, and sometimes in lightweight aggregate; collected as a volcanic specimen.
Geological facts
Vesicles can later fill with secondary minerals, forming amygdaloidal basalt.
Field identification & locations
Common near volcanic flows and cinder fields; identify by its dark fine-grained matrix and scattered rounded holes. The image alone cannot confirm composition or locality.
