A subgroup is the andalusite, staurolite, kyanite and sillimanite-schists which usually make their appearance in the vicinity of gneissose granites, and have presumably been affected by contact metamorphism.
Where the schists of sedimentary origin have been pierced by these igneous intrusions, they are charged with contact minerals such as sillimanite, cordierite, kyanite and andalusite.
