igneous
Weathered basalt pebble
Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase, pyroxene, and commonly olivine or iron oxides
AI-generated identification · may be incorrectTypically dark gray to brown, fine-grained, dull to subtly granular, with no visible cleavage; hardness about 5–6 Mohs and specific gravity roughly 2.8–3.0. The rounded shape and brown surface indicate abrasion and weathering, possibly with iron-oxide staining.
Identified More igneous →
Explore Weathered basalt pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically dark gray to brown, fine-grained, dull to subtly granular, with no visible cleavage; hardness about 5–6 Mohs and specific gravity roughly 2.8–3.0. The rounded shape and brown surface indicate abrasion and weathering, possibly with iron-oxide staining.
Formation & geological history
Formed when mafic lava cooled rapidly at or near Earth’s surface, commonly in oceanic crust, volcanic fields, and flood-basalt provinces; individual cooling ages range from recent to billions of years.
Uses & applications
Used as crushed aggregate, road stone, riprap, and sometimes architectural stone; this small, ordinary pebble has minimal jewelry or collector value.
Geological facts
Basalt is the most abundant volcanic rock and makes up much of the ocean floor. It may be weakly magnetic if it contains magnetite.
Field identification & locations
Identify it by its dark color, compact fine texture, heavy feel, and lack of obvious quartz or large crystals; a streak, magnet, and fresh-break examination would help confirm it. Common worldwide in volcanic and river environments.
