igneous
Weathered dark-gray pebble
Likely basalt or a basaltic volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectFine-grained, dull to weakly earthy luster, gray-brown weathered surface, and no obvious crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1. The rounded shape indicates water or sediment abrasion.
Identified More igneous →
Explore Weathered dark-gray pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Fine-grained, dull to weakly earthy luster, gray-brown weathered surface, and no obvious crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1. The rounded shape indicates water or sediment abrasion.
Formation & geological history
Probably an eroded volcanic rock formed when basaltic lava cooled rapidly at or near Earth’s surface, generally in the Cenozoic or older depending on locality. Its precise age and source cannot be determined visually.
Uses & applications
Common basalt is used as aggregate, road material, building stone, and occasionally as a decorative specimen; this small pebble has negligible commercial value.
Geological facts
Basalt commonly contains plagioclase, pyroxene, and sometimes olivine or magnetite. A magnet may attract it weakly if magnetite is abundant.
Field identification & locations
Look for a dense, fine-grained texture, dark color, and lack of visible layering; test for weak magnetism and hardness against glass. Common in volcanic regions, streambeds, beaches, and glacial deposits.
