igneous
Tumbled dark banded stone, possibly indigo gabbro or banded basalt
Indeterminate; likely fine-grained mafic rock composed mainly of plagioclase and pyroxene, with possible amphibole or alteration minerals
AI-generated identification · may be incorrectDark gray to black, rounded and polished, with subtle lighter flow-like bands; likely dull to weakly vitreous luster, hardness about 5–6 Mohs, massive structure, and no visible cleavage. The photograph is insufficient for confident mineral identification.
Identified More igneous →
Explore Tumbled dark banded stone, possibly indigo gabbro or banded basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, rounded and polished, with subtle lighter flow-like bands; likely dull to weakly vitreous luster, hardness about 5–6 Mohs, massive structure, and no visible cleavage. The photograph is insufficient for confident mineral identification.
Formation & geological history
Likely formed from cooling mafic magma or lava, with banding produced by mineral segregation or flow textures; age and locality cannot be determined visually. It may also be a commercial tumbled “indigo gabbro” or similar dark decorative stone.
Uses & applications
Used mainly as a tumbled specimen, paperweight, or craft material; not typically valuable for construction in this small form and generally unsuitable for fine jewelry. Common commercial pieces sell as decorative stones.
Geological facts
The smooth surface indicates human tumbling and polishing, which obscures diagnostic textures. A streak test, hardness test, specific gravity, and close inspection of fresh edges would improve identification.
Field identification & locations
Commonly sourced from basaltic or gabbroic deposits worldwide; identify by its high density, dark color, and hardness, while distinguishing it from glass or slag through a granular texture and non-conchoidal fracture.
