Heating of a solid to a temperature below its melting point to bring about a state of thermal decomposition or a phase transition other than melting. Included are the following types of reactions: (1) thermal dissociation, including destructive distillation of organic compounds, e.g., concentration of aluminum by heating of bauxite; (2) polymorphic phase transitions, e.g., conversion of anatase to rutile form of TiO2; (3) thermal recrystallization, e.g., devitrification of glass. Calcination is often used in the beneficiation of ores.See Destructive Distillation; Pyrolysis.