igneous
Vesicular basalt (probable iron-rich volcanic rock)
Basalt; chiefly plagioclase, clinopyroxene, olivine, and Fe-Ti oxides
AI-generated identification · may be incorrectDark gray to black, fine-grained and locally vesicular, with dull to submetallic patches likely iron oxides or weathered sulfides. Mohs hardness about 5–6; generally massive, with no obvious cleavage; specific gravity commonly 2.8–3.1.
Identified More igneous →
Explore Vesicular basalt (probable iron-rich volcanic rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained and locally vesicular, with dull to submetallic patches likely iron oxides or weathered sulfides. Mohs hardness about 5–6; generally massive, with no obvious cleavage; specific gravity commonly 2.8–3.1.
Formation & geological history
Formed when low-silica basaltic lava cooled rapidly at or near Earth’s surface, producing a fine matrix and gas bubbles; commonly Cenozoic or younger, though basalt occurs throughout geologic time. The rusty brown areas reflect surface oxidation and weathering.
Uses & applications
Used as crushed aggregate, road metal, riprap, and occasionally dimension stone; ordinary specimens have little jewelry value.
Geological facts
Vesicles distinguish it from many dense igneous rocks, while the dark metallic-looking grains may be magnetite or ilmenite. A magnet test can help confirm abundant iron oxides, but the image alone cannot establish whether it is basalt, scoria, or slag.
Field identification & locations
Common in volcanic regions, oceanic crust, flood-basalt provinces, and cinder fields worldwide. Test for a fine crystalline texture, bubbles, gray-black color, and magnetic response; man-made slag is a possible look-alike.
