metamorphic

Polished dark granite (likely gneiss or granitic gneiss)

Quartz–feldspar–biotite granite/gneiss; exact identification requires examination of the specimen

AI-generated identification · may be incorrect

Coarse-grained, dark gray to black with pale mineral flecks and possible rusty weathering along the edge; visible grains suggest quartz, feldspar, and dark mica. Typical hardness is about 6–7 Mohs; minerals have a vitreous to pearly luster, with no obvious cleavage at this scale.

Identified October 13, 2026More metamorphic →

Explore Polished dark granite (likely gneiss or granitic gneiss) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Granite forms when silica-rich magma cools slowly underground; gneiss forms when such rocks are recrystallized and often banded by heat and pressure. These processes span many geological ages, and the image alone cannot establish which rock or age applies.

Uses & applications

Polished specimens are used for décor and collecting; granite is also widely used in countertops, paving, and building stone.

Geological facts

The rounded, glossy surface appears mechanically polished, which can obscure grain boundaries and any gneissic banding.

Field identification & locations

Look for interlocking pale quartz/feldspar grains and dark biotite; gneiss commonly shows mineral bands, while granite is more uniformly speckled. Common worldwide in continental crust and ancient mountain belts.