metamorphic

Probable gneiss

Banding-scale metamorphic rock composed mainly of quartz, feldspar, and mica; possibly granitic gneiss

AI-generated identification · may be incorrect

Gray-blue, coarse-grained, and weakly foliated with irregular light and dark mineral bands; quartz and feldspar have a vitreous luster, while mica may appear pearly. Typical hardness is about 6–7 Mohs, with no obvious cleavage as a whole rock and specific gravity around 2.6–2.8.

Identified September 22, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when granite or another felsic protolith underwent high-grade regional metamorphism, producing mineral segregation and foliation. Such rocks commonly formed during Precambrian to Paleozoic mountain-building events, though exact age requires laboratory analysis.

Uses & applications

Used as dimension stone, architectural facing, landscaping stone, aggregate, and decorative specimens; attractive pieces may be polished.

Geological facts

The image could also represent a weathered granite or granitic schist, since the specimen shows limited visible banding and lacks a scale reference.

Field identification & locations

Look for alternating quartz–feldspar-rich light zones and darker biotite/amphibole-rich layers, interlocking grains, and a hard, scratch-resistant surface. Common in ancient continental shields and metamorphic mountain belts.