metamorphic
Gneiss (Augen Gneiss)
Augen Gneiss
Hardness: 6-7 (Mohs scale); Color: Gray to white with dark striations; Luster: Dull to pearly; Structure: Foliated with characteristic eye-shaped mineral grains (augen); Cleavage: Poor, splits into uneven layers.
- Hardness
- 6-7 (Mohs scale)
- Color
- Gray to white with dark striations
- Luster
- Dull to pearly
Identified More metamorphic →
Explore Gneiss (Augen Gneiss) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: Gray to white with dark striations; Luster: Dull to pearly; Structure: Foliated with characteristic eye-shaped mineral grains (augen); Cleavage: Poor, splits into uneven layers.
Formation & geological history
Formed through high-grade regional metamorphism of igneous (granite) or sedimentary rocks under extreme heat and pressure, typically during mountain-building events (orogenies).
Uses & applications
Used primarily in heavy construction as crushed stone or road base, and as decorative dimension stone for countertops and building facades.
Geological facts
The word 'augen' comes from the German word for 'eyes,' referring to the large, eye-shaped feldspar crystals that resist deformation during the metamorphic process.
Field identification & locations
Look for distinct banding or foliation with larger mineral 'clasts' wrapped in a fine-grained matrix. Common in ancient crystalline basement shields like the Canadian Shield or the Appalachians.
More like this
