metamorphic

Banded gneiss, possibly garnet-bearing

Foliated gneiss; predominantly quartz–feldspar–mica, with possible amphibole or garnet

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; gray, white, black, and greenish bands with sparkly mica; vitreous to pearly luster, granular crystals, and weak cleavage inherited from mica. The pronounced compositional banding and folded foliation are diagnostic.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when preexisting igneous or sedimentary rock underwent high-grade regional metamorphism, commonly at roughly 600–800°C and deep crustal pressures. Such gneisses may range from Precambrian to younger Paleozoic orogenic ages; the exact age requires laboratory analysis.

Uses & applications

Used as dimension stone, facing stone, landscaping rock, and aggregate; attractive polished pieces are collected as decorative specimens. It is generally less suitable than granite for uniform countertops because of its foliation.

Geological facts

The swirling bands record intense ductile deformation and mineral segregation during mountain building. Green areas may reflect epidote, chlorite, or amphibole rather than a separate gemstone.

Field identification & locations

Identify it by alternating light quartz–feldspar and dark mica/amphibole bands, foliation, and a coarse crystalline texture; it commonly occurs in continental mountain belts and exposed Precambrian shields.