metamorphic

Granite-like gneiss

Foliated quartz–feldspar–mica gneiss, possibly granitic protolith

AI-generated identification · may be incorrect

Medium- to coarse-grained, gray and brown, with quartz, feldspar, and dark mica; vitreous quartz, uneven granular texture, and weak compositional banding. Hardness is approximately 6–7 Mohs; cleavage is poor overall, with feldspar cleavage locally visible; specific gravity about 2.6–2.8.

Identified September 1, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when granitic or sedimentary rock underwent high-grade regional metamorphism, recrystallizing under intense heat and pressure; its exact geological age cannot be determined from the photograph. Common in Precambrian continental shields and mountain belts.

Uses & applications

Used locally as dimension stone, landscaping rock, aggregate, and building stone; attractive polished pieces may be used decoratively, but this irregular specimen has little gem value.

Geological facts

The speckled appearance reflects interlocking quartz and feldspar grains with dark biotite or hornblende. Gneiss commonly preserves evidence of deep crustal burial and tectonic deformation.

Field identification & locations

Identify it by its hard, interlocking grains and subtle light-dark mineral segregation; granite lacks metamorphic banding, while schist is usually much more strongly micaceous and foliated. Common worldwide in ancient crystalline terrains.