Crocus
Sesquioxide of iron used with oil for polishing brass and steel work. Crystals of sulphate of iron are subjected to a great heat, and then graded into polishing powders of various degrees of fineness. The more calcined part is of a bluish purple color, coarser and harder than the less calcined and is known as crocus. The less calcined and finer portion is of a scarlet color and is known as rouge.