The nuclearity and structure of aluminum cations generated by the hydrolysis of aluminum salt solutions depends markedly on the method of preparation. This speciation affects not only the thermochemistry of processes leading to ceramics, but the microstructures of the ceramics themselves. A brief review of aluminum ion hydrolysis is presented along with a study of the thermal evolution of gels derived from aluminum salt solutions via several different hydrolysis methods. The observation of 5 - coordinate aluminum in a bulk transition alumina by MAS-NMR is reported. A new, high defect precursor of η-alumina dubbed “high-5 alumina” is described and the far reaching implications of this discovery are discussed.