metamorphic
Foliated Gneiss
Gneiss (Metamorphic Rock)
Hardness: 6-7 (Mohs scale), Color: Banded white, green, and red/brown, Luster: Dull to pearly, Structure: Foliated with distinct compositional banding, SG: 2.6-2.9
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Banded white, green, and red/brown, Luster: Dull to pearly, Structure: Foliated with distinct compositional banding, SG: 2.6-2.9
Formation & geological history
Formed through high-grade regional metamorphism of igneous or sedimentary protoliths under extreme heat and pressure, typically deep within the Earth's crust during mountain-building events.
Uses & applications
Used primarily as decorative crushed stone, dimension stone for flooring and facades, and as an ornamental specimen for collectors.
Geological facts
Gneiss is some of the oldest rock found on Earth, with the Acasta Gneiss in Canada dating back approximately 4 billion years.
Field identification & locations
Identified by its characteristic 'gneissose banding' where minerals separate into alternating light and dark layers. Commonly found in the roots of eroded mountain ranges.
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