Cr micas identified as chrome phengites occur in association with other Cr-rich minerals in a peculiar schist which lies along a complex shear zone within the pre-Caledonian Erris Complex. The schist generally has a chaotic internal structure but locally there is a crude planar mineralogical zoning with a serpentinebearing zone structurally above a Cr mica zone. Chemical analyses indicate that the schist is a tectonic derivative of a mixture of rock with a pronounced metasomatic character.