metamorphic

Banded gneiss

Gneiss, a foliated metamorphic rock; likely quartz–feldspar–mica gneiss

AI-generated identification · may be incorrect

Distinct alternating light and dark mineral bands, with a coarse, crystalline texture. Typically contains quartz and feldspar with dark biotite or amphibole; hardness is about 6–7 Mohs, and the minerals have vitreous to pearly luster.

Identified October 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when pre-existing igneous or sedimentary rock is recrystallized and segregated into bands under high heat and pressure. Gneiss occurs in ancient continental crust, often billions of years old; this specimen’s age cannot be determined from the photo.

Uses & applications

Used as dimension stone, paving, and landscaping material; attractive banded pieces are collected or used decoratively.

Geological facts

Gneissic banding reflects mineral separation during metamorphism, not sedimentary layering.

Field identification & locations

Identify it by coarse, alternating light and dark bands and crystalline grains; it is common in old continental shields and mountain belts. The visible banding supports gneiss, though a photo cannot establish its exact mineral composition.