igneous
Polished dark-and-light speckled stone, likely gabbro or diorite
Likely gabbro or diorite; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectCoarse, mottled black, gray, and cream crystals with a dull to slightly polished luster; likely Mohs hardness 6–7 and no obvious cleavage. Gabbro is typically plagioclase plus pyroxene; diorite is plagioclase plus hornblende or biotite.
Identified More igneous →
Explore Polished dark-and-light speckled stone, likely gabbro or diorite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, mottled black, gray, and cream crystals with a dull to slightly polished luster; likely Mohs hardness 6–7 and no obvious cleavage. Gabbro is typically plagioclase plus pyroxene; diorite is plagioclase plus hornblende or biotite.
Formation & geological history
An intrusive igneous rock formed as magma cooled slowly underground, allowing visible crystals to grow. Such rocks occur in ancient continental crust and in exposed plutons of many geological ages.
Uses & applications
Commonly used as crushed aggregate, paving, dimension stone, and decorative material; polished pieces may be collected or used in crafts.
Geological facts
The light-and-dark pattern reflects contrasting mineral grains rather than layering. A definitive distinction between gabbro and diorite generally requires identifying the minerals and estimating plagioclase composition.
Field identification & locations
Look for interlocking, visible light feldspar and dark mafic crystals, with no sedimentary layers or foliation. A hardness test and close inspection of crystal minerals can help distinguish it; similar stones occur worldwide in igneous intrusions.
