igneous
Vesicular basalt (likely scoriaceous basalt)
Basalt; chiefly plagioclase, clinopyroxene, and olivine, with iron-titanium oxides
AI-generated identification · may be incorrectDark gray to black, fine-grained, dull to slightly vitreous, with abundant irregular vesicles and rough fracture surfaces. Hardness is about 6 on Mohs scale; it has no prominent cleavage and typical specific gravity of 2.7–3.0.
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Physical properties
Dark gray to black, fine-grained, dull to slightly vitreous, with abundant irregular vesicles and rough fracture surfaces. Hardness is about 6 on Mohs scale; it has no prominent cleavage and typical specific gravity of 2.7–3.0.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near Earth’s surface, with trapped gas producing the cavities. Most examples are geologically young compared with continental crust, ranging from recent lava flows to rocks billions of years old.
Uses & applications
Used as crushed aggregate, road base, riprap, railroad ballast, and landscaping stone; attractive pieces may be collected but are rarely used in jewelry.
Geological facts
The porous texture indicates gas-rich lava, though the specimen is denser and darker than typical red scoria. It may also be termed vesicular basalt when the vesicles are relatively sparse or irregular.
Field identification & locations
Identify it by its black color, very fine matrix, uneven vesicles, and heavy weight; it will not fizz with dilute acid and commonly scratches glass. Common settings include volcanic islands, lava plateaus, and cinder cones.
