igneous
Rounded river pebble, likely basaltic or andesitic rock
Fine-grained mafic to intermediate volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectDark olive-brown, dull to slightly earthy luster, rounded and water-worn, with very fine-grained texture and no visible crystals. Likely Mohs hardness about 5–6; cleavage absent; specific gravity approximately 2.7–3.0.
Identified More igneous →
Explore Rounded river pebble, likely basaltic or andesitic rock in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark olive-brown, dull to slightly earthy luster, rounded and water-worn, with very fine-grained texture and no visible crystals. Likely Mohs hardness about 5–6; cleavage absent; specific gravity approximately 2.7–3.0.
Formation & geological history
Probably formed as lava that cooled rapidly at or near Earth’s surface, then was rounded by stream or beach abrasion. Its precise geological age and formation location cannot be determined from the photograph.
Uses & applications
Typically used as landscaping stone, decorative aggregate, or a teaching/collecting specimen; not generally valuable as a gemstone.
Geological facts
The brown surface may reflect weathering, iron-oxide staining, or a thin alteration rind rather than the rock’s fresh interior color.
Field identification & locations
Common in volcanic terrains and river gravels worldwide. A fresh broken surface, streak, magnet test, acid test, and hand-lens examination could distinguish basalt, andesite, and weathered sedimentary alternatives.
