igneous
Vesicular basalt (likely weathered basalt)
Basalt; primarily plagioclase, clinopyroxene, and Fe-Ti oxides
AI-generated identification · may be incorrectDark gray, fine-grained, dull to slightly waxy; abundant rounded vesicles and possible small zeolite/mineral infillings. Hardness about 5–6 Mohs, no obvious cleavage, dense but porous, with an aphanitic texture.
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Physical properties
Dark gray, fine-grained, dull to slightly waxy; abundant rounded vesicles and possible small zeolite/mineral infillings. Hardness about 5–6 Mohs, no obvious cleavage, dense but porous, with an aphanitic texture.
Formation & geological history
An extrusive igneous rock formed when mafic lava cooled rapidly at or near Earth’s surface, commonly during volcanic eruptions. Basalt ranges from Precambrian to modern age; the specimen’s age and locality cannot be determined from the photo.
Uses & applications
Used as crushed aggregate, road stone, riprap, and occasionally decorative stone; attractive vesicular pieces are collected but generally have little gem value.
Geological facts
The cavities formed from gas bubbles trapped in cooling lava; later groundwater may deposit pale zeolites, calcite, or silica inside them.
Field identification & locations
Common in volcanic regions, oceanic crust, Hawaii, Iceland, India, and the Columbia River Basalt Province. Confirm with a fresh surface, magnetic response, and hardness; scoria is lighter and more highly vesicular.
