Crystallization of stilpnomelane and pumpellyite, disappearance of prehnite and development of assemblages containing the pair pumpellyite‐actinolite, and disappearance of pumpellyite, define isograds separating four zones of progressive regional metamorphism in the Nambucca Slate Belt of northeastern New South Wales. Mineralogical changes are paralleled by textural changes in metaclastic rocks. Detrital grains are progressively modified, a preferred orientation of material becomes increasingly perfected, and a foliation develops as grade increases.