igneous
Basalt (probable)
Basalt; chiefly plagioclase feldspar, pyroxene, and minor olivine or magnetite
AI-generated identification · may be incorrectDark gray-black, fine-grained, massive, and dull to weakly vitreous; typically Mohs 5–6, with no visible cleavage and specific gravity about 2.8–3.0. The rounded, glossy surface may reflect weathering, polishing, or a basaltic glass-rich texture.
Identified More igneous →
Explore Basalt (probable) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, fine-grained, massive, and dull to weakly vitreous; typically Mohs 5–6, with no visible cleavage and specific gravity about 2.8–3.0. The rounded, glossy surface may reflect weathering, polishing, or a basaltic glass-rich texture.
Formation & geological history
An extrusive igneous rock formed when mafic lava cooled rapidly at or near Earth’s surface, commonly during the Cenozoic or older volcanic episodes. Exact age and locality cannot be determined from the photograph.
Uses & applications
Used extensively as crushed aggregate, road stone, riprap, paving, and construction material; attractive dense pieces may be collected or polished, but this specimen has little commercial value.
Geological facts
Basalt is the most widespread volcanic rock on Earth and forms much of the oceanic crust. Vesicles, if present, may later fill with minerals such as zeolite, calcite, or quartz.
Field identification & locations
Identify by its uniformly dark color, fine texture, heaviness, and lack of obvious large crystals; a streak test, magnetism test, and fresh broken surface would help distinguish it from slag or dark sedimentary rock. Common in volcanic regions and oceanic-island terrains.
