metamorphic
Banded Gneiss
Gneiss (Metamorphic Rock)
Hardness: 6-7 (Mohs); Color: Gray, tan, brown, and reddish iron staining; Luster: Dull to slightly vitreous; Structure: Foliated with distinct compositional banding (gneissose banding); Gravity: 2.6-2.9
- Hardness
- 6-7 (Mohs)
- Color
- Gray, tan, brown, and reddish iron staining
- Luster
- Dull to slightly 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 (Mohs); Color: Gray, tan, brown, and reddish iron staining; Luster: Dull to slightly vitreous; Structure: Foliated with distinct compositional banding (gneissose banding); Gravity: 2.6-2.9
Formation & geological history
Formed through high-grade regional metamorphism of igneous or sedimentary protoliths under intense temperature and pressure, typically during mountain-building events (orogeny).
Uses & applications
Primarily used as crushed stone for road construction and aggregate; high-quality pieces are used as dimension stone for counter tops, flooring, and decorative cladding.
Geological facts
Gneiss contains some of the oldest rocks on Earth, such as the Acasta Gneiss in Canada, which is approximately 4 billion years old.
Field identification & locations
Identify by looking for 'segregated' bands of different minerals (light vs. dark) and a coarse-grained texture. It does not split easily along planes like schist. Common in the roots of mountain ranges and stable continental shields.
More like this
