metamorphic
Granitic Gneiss
Gneiss (High-grade metamorphic rock)
Hardness of 6-7 on the Mohs scale; distinctive alternating light and dark mineral bands (gneissic banding); color ranges from pink/grey to black; sub-to-vitreous luster; specific gravity of 2.6-2.9.
Identified More metamorphic →
Explore Granitic Gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6-7 on the Mohs scale; distinctive alternating light and dark mineral bands (gneissic banding); color ranges from pink/grey to black; sub-to-vitreous luster; specific gravity of 2.6-2.9.
Formation & geological history
Formed by high-temperature and high-pressure metamorphic processes altering pre-existing igneous or sedimentary rocks (such as granite or shale), typically during regional mountain-building events.
Uses & applications
Used in construction, as crushed stone for roadbeds, building facades, dimension stone, and countertops.
Geological facts
Gneiss contains some of the oldest known rock material on Earth, with certain zircon crystals within gneiss formations dating back over 4 billion years.
Field identification & locations
Easily identified in the field by its striking alternating light (quartz/feldspar) and dark (biotite/amphibole) bands, known as banding or lineation.
More like this
