igneous
Dark rounded stone, likely basalt pebble
Basalt, predominantly plagioclase and pyroxene; exact identification is uncertain from the image
AI-generated identification · may be incorrectFine-grained, dark gray to black, dull to weakly vitreous luster, with no visible crystals or cleavage; hardness about 6 on the Mohs scale and specific gravity roughly 2.8–3.0. Its smooth, flattened shape suggests water-worn or tumbled basalt.
Identified More igneous →
Explore Dark rounded stone, likely basalt pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Fine-grained, dark gray to black, dull to weakly vitreous luster, with no visible crystals or cleavage; hardness about 6 on the Mohs scale and specific gravity roughly 2.8–3.0. Its smooth, flattened shape suggests water-worn or tumbled basalt.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava rapidly cools at or near Earth’s surface, commonly in volcanic fields and oceanic crust. Individual pebbles may be geologically ancient, but their rounded shape reflects later erosion and transport.
Uses & applications
Used as aggregate, road base, riprap, paving stone, and occasionally decorative material; an ordinary pebble has little jewelry value.
Geological facts
Basalt is the most abundant volcanic rock on Earth and makes up much of the ocean floor. It may be weakly magnetic if it contains magnetite.
Field identification & locations
Common in volcanic and river environments; identify by its uniform dark color, fine texture, substantial weight, and lack of visible layering. A streak, magnetism test, and fresh broken surface would improve identification.
