The beudantite subgroup has the general formula AB3(XO4)(SO4)(OH)6, the crandallite subgroup AB3(TO4)2(OH)5.H2O and the florencite subgroup AB3(TO4)2(OH)5or6.
V alunitovi podskupini je B aluminij (Al), v jarozitovi podskupini pa Fe3+.