metamorphic

Gneiss

Metamorphic Gneiss

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: reddish-brown with whitish speckling and banding; Luster: earthy to dull with slight vitreous sparkle from quartz/feldspar; Cleavage: poor/irregular fracture; Specific Gravity: 2.6 - 2.9

Hardness: 6-7 on Mohs scale
Color: reddish-brown with whitish speckling and banding

Identified July 24, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed through high-grade regional metamorphism of igneous (like granite) or sedimentary rocks under extreme heat and pressure deep within Earth's crust.

Uses & applications

Used in construction as crushed stone, dimension stone for buildings and countertops, landscape rock, and educational geological specimens.

Geological facts

Gneissic banding is a distinct texture where light-colored quartz and feldspar alternate with dark-colored amphibole or mica minerals due to directional stress during metamorphic processes.

Field identification & locations

Identified by distinct light and dark mineral segregation (gneissic foliation) and crystalline coarse-grained texture. Extremely common in ancient shield areas worldwide like North America and Scandinavia.