metamorphic

Banded Gneiss

Gneiss (Metamorphic rock predominantly containing quartz, feldspar, and mica)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Gray, black, and white bands; Luster: Dull to slightly pearly; Crystal structure: Coarse-grained foliated texture with distinct alternating layers of light and dark minerals.

Hardness: 6-7 on Mohs scale
Color: Gray, black, and white bands
Luster: Dull to slightly pearly

Identified July 20, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks at extreme temperatures and pressures deep within the Earth's crust, often during mountain-building events.

Uses & applications

Used primarily as a decorative stone in landscaping, aquarium decor, and sometimes as crushed stone for road construction or high-end building veneer.

Geological facts

Gneiss is some of the oldest rock found on Earth, with the Acasta Gneiss in Canada dating back over 4 billion years. The banding is caused by the segregation of minerals during intense pressure.

Field identification & locations

Identify by looking for 'gneissose banding' consisting of alternating light (quartz/feldspar) and dark (biotite/amphibole) mineral layers. Commonly found in glaciated riverbeds or mountain ranges.