Publisher Summary This chapter focuses on sodium sulfate deposits and discusses the way in which a commercial product is derived from them. The initial processing of the ore is varied for different deposits. Over the years, the processing of natural sodium sulfate has undergone a transition of two different types. Initially, it was often produced from comparatively small deposits on a limited scale, while now, predominantly large deposits are employed, and the production capacity of the average plant is very high. The chapter indicates that the first of the higher purity processing systems to be used in Canada was called “brining.” There is still some production being practiced in the earlier mode to satisfy local needs, but most of the world's production is now recovered from the largest of the deposits, and well over 95% is produced in large, efficient plants.