The metamorphism surrounding the granite of Carn Chuinneag in eastern Ross-shire provides the classical example of polymetamorphism in which a regional metamorphism is superimposed on a normal thermal metamorphism.

Prior to the regional alteration a pelitic facies of the Moine sediments suffered metamorphism of a purely thermal type in the vicinity of the granite. At a subsequent date the whole region was involved in fold movements with the production of crystalline schists. In this deformation the belt of rocks surrounding the granite yielded in such a way that belts of the hornfels zone moved en masse and are preserved amidst rocks which are now typical crystalline schists, and all stages of transition between genuine hornfelses and typical micaschists can be traced in the field.