metamorphic

Biotite-bearing gneiss

Feldspar–quartz gneiss with dark biotite or amphibole-rich band

AI-generated identification · may be incorrect

Coarse-grained, strongly foliated rock with alternating pale quartz/feldspar and dark mineral bands. Quartz and feldspar have Mohs hardness about 6–7; dark biotite is about 2.5–3, with a shiny to dull luster and platy cleavage. Exact minerals are difficult to confirm from the blurred image.

Identified September 30, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when pre-existing rock was recrystallized and segregated into mineral bands under high heat and pressure during regional metamorphism. Gneisses occur in ancient continental basement, commonly Precambrian, though age cannot be determined from the image.

Uses & applications

Used as building and facing stone, paving, landscaping stone, and sometimes as a decorative dimension stone.

Geological facts

Gneissic banding reflects mineral segregation during metamorphism; unlike sedimentary layering, it is typically produced by deformation and recrystallization.

Field identification & locations

Look for coarse, interlocking crystals and persistent light-and-dark bands. Gneiss is widespread in metamorphic belts and exposed continental shields; the photo alone does not establish a precise locality or mineral identification.