igneous
Vesicular basalt
Basalt, primarily plagioclase feldspar, pyroxene, and often olivine
AI-generated identification · may be incorrectDark gray, fine-grained and porous with a dull to slightly glassy luster; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.8–3.0. The cavities are gas vesicles, though the specimen may also contain weathering or mineral-filled pores.
Identified More igneous →
Explore Vesicular basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray, fine-grained and porous with a dull to slightly glassy luster; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.8–3.0. The cavities are gas vesicles, though the specimen may also contain weathering or mineral-filled pores.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near Earth’s surface, commonly during the Cenozoic or younger volcanic eruptions. Its exact age cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, road metal, concrete and asphalt stone, riprap, and building stone; attractive polished pieces are occasionally collected. Common specimens generally have little commercial value.
Geological facts
Basalt is the most abundant volcanic rock on oceanic crust and commonly forms lava flows, dikes, and ocean-floor pillow lavas. Vesicles record bubbles trapped during lava cooling.
Field identification & locations
Identify it by its dense dark-gray color, fine texture, irregular fracture, and small holes; it is heavier than pumice and lacks pumice’s frothy, lightweight structure. Common worldwide, especially in volcanic regions and oceanic crust.
