Abstract: Red mud from alumina plants, normally considered useless waste, is made into useful ceramics articles by mixing 51-90% by weight of red mud with 10-49% by weight of at least one mineral and/or silicate containing material, shaping the mixture and firing it at a temperature of 950.degree.-1250.degree. C.

Abstract: The invention concerns a process for solubilizing alumina in minerals, rocks or industrial waste products, in which the starting material in finely divided form is mixed with lime in an amount 1 to 3 moles or more of lime (CaO or Ca(OH).sub.2) for each mole of alumina and optionally 1 mole for each mole of any silica present in the starting material, and at the same time or thereafter with water, the resulting mix is maintained under hydrothermal conditions until the alumina has become solubilized by reaction with the lime, and the product is if necessary comminuted to bring it to a form suitable for leaching out of the solubilized alumina.