igneous
Rounded basalt pebble
Basalt; primarily plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectFine-grained, dark gray-green, dull to weakly earthy luster, with no visible crystals; Mohs hardness about 6, tough and commonly very dense. The rounded shape and smooth surface indicate water or sediment abrasion.
Identified More igneous →
Explore Rounded 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-green, dull to weakly earthy luster, with no visible crystals; Mohs hardness about 6, tough and commonly very dense. The rounded shape and smooth surface indicate water or sediment abrasion.
Formation & geological history
Basalt forms when low-silica basaltic lava rapidly cools at or near Earth’s surface, commonly in volcanic fields, oceanic crust, and flood-basalt provinces. Its exact age cannot be determined from the image and may range from recent to billions of years old.
Uses & applications
Used as crushed aggregate, road base, railway ballast, riprap, and building stone; attractive pieces may be used as landscaping or teaching specimens. This small, ordinary pebble has minimal collector value.
Geological facts
Basalt is the most abundant volcanic rock and makes up much of the ocean floor. Vesicles, if present, may indicate gas-rich lava, but none are clearly visible here.
Field identification & locations
Identify by its dark color, fine texture, high density, and lack of obvious layering or large crystals; a streak, magnetism, and fresh fracture can help distinguish it from other dark pebbles. Common near volcanic terrain and river or beach gravels.
