metamorphic
Gneiss
High-grade Metamorphic Gneiss
Hardness: 6-7 on Mohs scale. Color: Gray, white, or light green with dark streaks. Luster: Dull to pearly. Crystal Structure: Coarse-grained with a foliated, banded texture. Specific Gravity: 2.6-2.9.
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, white, or light green with dark streaks
- Luster
- Dull to pearly
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale. Color: Gray, white, or light green with dark streaks. Luster: Dull to pearly. Crystal Structure: Coarse-grained with a foliated, banded texture. Specific Gravity: 2.6-2.9.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under extreme heat and pressure. This specimen shows significant compression and recrystalization.
Uses & applications
Commonly used as crushed stone in road construction or as decorative dimension stone for countertops and building facades.
Geological facts
Gneiss is one of the oldest rock types found on Earth, with some specimens from the Acasta Gneiss complex dating back over 4 billion years.
Field identification & locations
Identified by distinct light and dark mineral bands (gneissose banding). Look for alternating layers of quartz/feldspar and darker minerals like hornblende or mica. Commonly found in mountainous regions or glacial deposits.
More like this
