Gneiss
/naɪs/
Definition 1 of 1
Pro Tip 1/3Layered Rock
Gneiss is known for its banded or layered appearance, which is helpful to mention when describing its looks. 
The layered structure of the gneiss was clearly visible on the cliff face.
Pro Tip 2/3Technical Term
The use of 'gneiss' is often technical, found in geology context, so it might not be widely recognized outside this field. 
During our geology class, we studied how gneiss forms under high pressure.
Pro Tip 3/3Mineral Content
You can emphasize the specific types of minerals in gneiss such as quartz or feldspar to convey its composition. 
The gneiss sample contained significant amounts of quartz and feldspar, giving it a unique texture.