Which of the following does not represent an alum?

Alum is an inorganic chemical compound that typically consists of sulphates, water molecules, and one or more metals, usually aluminium. Alum is essentially an aluminum double sulphate salt that has been hydrated. Alum has the typical chemical formula $\mathrm{XAl} {\left({\mathrm{SO}}_4\right)}_2.12\mathrm{H}2\mathrm{O}$. Mineral alums are a possibility. Leucite and alunite, for instance.