igneous
Polished dark pebble, possibly basalt
Basalt (fine-grained mafic volcanic rock; identification from the image is uncertain)
AI-generated identification · may be incorrectSmooth, rounded, dark gray to black surface with a subdued luster and small pits or pale specks. Basalt typically has Mohs hardness 5–6, a fine-grained texture, and no visible cleavage.
Identified More igneous →
Explore Polished dark pebble, possibly basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Smooth, rounded, dark gray to black surface with a subdued luster and small pits or pale specks. Basalt typically has Mohs hardness 5–6, a fine-grained texture, and no visible cleavage.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface; basalt occurs from ancient to recent geological periods. The rounded shape suggests water abrasion or deliberate tumbling.
Uses & applications
Commonly used as crushed aggregate, paving stone, and decorative landscaping material; polished pebbles are also used in crafts and collections.
Geological facts
Basalt is one of Earth’s most widespread volcanic rocks and also forms much of the ocean floor.
Field identification & locations
A dark, fine-grained pebble with no obvious crystals is consistent with basalt, but the photo cannot confirm its composition; similar-looking rocks include andesite and dark river stones. Basalt is widespread worldwide, especially in volcanic regions.
