igneous
Dark, fine-grained rock pebble (likely basalt)
Basalt; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray-brown, dull, and fine-grained, with scattered light-colored mineral grains or spots. Basalt is typically composed of plagioclase and pyroxene, sometimes olivine; hardness about 6 on Mohs scale, with no obvious cleavage and a specific gravity near 2.8–3.0.
Identified More igneous →
Explore Dark, fine-grained rock pebble (likely basalt) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, dull, and fine-grained, with scattered light-colored mineral grains or spots. Basalt is typically composed of plagioclase and pyroxene, sometimes olivine; hardness about 6 on Mohs scale, with no obvious cleavage and a specific gravity near 2.8–3.0.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface; its age and source cannot be determined from the image.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and construction material; attractive pieces may be collected or used decoratively.
Geological facts
Basalt is Earth’s most common volcanic rock and also forms much of the ocean floor.
Field identification & locations
A dark, dense pebble with a fine-grained texture and occasional pale crystals is consistent with basalt. A fresh broken surface or magnification would help distinguish it from other dark rocks.
