Gneiss is a protolith of migmatite.

Rock group Metamorphic
Metamorphism type Regional
Metamorphic rock class Metapelitic
Metabasic (mafic gneiss)
Granitic (granitic gneiss)
Protoliths Schist
Igneous rocks such
as granite

Gneiss in Hand Sample

Paleoproterozoic gneiss from Clear Creek Canyon, CO
Archean-aged basement complex gneiss from the Wyoming Craton
Biotitemuscovitegarnet Maidens gneiss (note that that’s four separate links)
Augen gneiss
Big honkin’ augen in Paleoproterozoic augen gneiss from Clear Creek Canyon, CO
Augen gneiss from Shetland
Folded Lewisian gneiss on a beach in Scotland

Gneiss in Thin Section

Maidens gneiss, plane polars
Maidens gneiss, crossed polars
Sillimanitegarnet gneiss, plane polars
Sillimanitegarnet gneiss, crossed polars
Augen gneiss, plane polars
Augen gneiss, crossed polars
Biotite gneiss, plane polars
Biotite gneiss, crossed polars

Sillimanite-garnet gneiss, plane polars

Sillimanite-garnet gneiss, crossed polars

Biotite gneiss, plane polars

Biotite gneiss, crossed polars