Results are presented of an investigation into the effect of the anion and cation of various catalytic additives on the mullite development in a Georgia Kaolin. The sodium and potassium compounds investigated were found to be poor catalysts. The calcium compounds were very good catalysts while the lithium compounds ranged from poor to very good for lithium chloride. It was found that the catalysis of mullite is affected by the anion although its effect is not as pronounced as that due to the cation.