metamorphic
Banded Gneiss
Gneiss (Metamorphic rock predominantly containing quartz, feldspar, and mica)
Hardness: 6-7 on Mohs scale; Color: Pink, grey, tan, and black bands; Luster: Dull to vitreous; Structure: Foliated with distinct compositional banding (gneissic banding); Cleavage: Poor, typically breaks along planes of weakness between bands.
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, grey, tan, and black bands
- Luster
- Dull to vitreous
Identified More metamorphic →
Explore Banded Gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, grey, tan, and black bands; Luster: Dull to vitreous; Structure: Foliated with distinct compositional banding (gneissic banding); Cleavage: Poor, typically breaks along planes of weakness between bands.
Formation & geological history
Formed through high-grade regional metamorphism of igneous (granite) or sedimentary (shale/mudstone) protoliths under extreme pressure and temperature conditions, often associated with mountain-building events.
Uses & applications
Used primarily in construction as crushed stone or dimension stone for countertops, flooring, and curbing. High-quality specimens are collected for geological study.
Geological facts
Gneiss is one of the oldest known rock types on Earth, with some specimens like the Acasta Gneiss dating back over 4 billion years. Its name comes from an Old High German word meaning 'sparkling'.
Field identification & locations
Identified by its 'zebra-stripe' appearance where light minerals (quartz/feldspar) and dark minerals (biotite/hornblende) separate into layers. Commonly found in the roots of mountain ranges and ancient continental shields.
More like this
