igneous
Vesicular basalt (likely scoriaceous basalt)
Mafic volcanic rock, chiefly plagioclase, pyroxene, and olivine; commonly iron-rich volcanic glass
AI-generated identification · may be incorrectDark brown to black, rough and porous, with dull to slightly vitreous luster; typically hardness 5–6, no prominent cleavage, fine-grained matrix, and low-to-moderate specific gravity reduced by vesicles.
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Physical properties
Dark brown to black, rough and porous, with dull to slightly vitreous luster; typically hardness 5–6, no prominent cleavage, fine-grained matrix, and low-to-moderate specific gravity reduced by vesicles.
Formation & geological history
Forms when gas-rich basaltic lava rapidly cools at or near the surface, trapping bubbles; usually Quaternary to Recent, though similar specimens occur throughout Earth’s volcanic history.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, and occasionally as an abrasive or barbecue-rock material; generally unsuitable for jewelry.
Geological facts
The bubbly texture is called vesicularity, and abundant vesicles produce scoria; denser, less porous material is termed basalt. The rusty-brown color commonly reflects oxidation of iron-bearing minerals.
Field identification & locations
Identify it by its black-to-brown color, volcanic texture, irregular vesicles, and lack of layering; common in lava fields, cinder cones, and volcanic islands worldwide. A hand lens can reveal tiny feldspar crystals.
