in Chemistry, denotes the formation of a kind of mealy powder on the surface of certain bodies. Efflorescence is occasioned either by decomposition or by drying. The efflorescence which happens to cobalt and martial pyrites is of the former; and that observed on the crystals of soda, Glauber's salt, and the like, of the latter kind. An efflorescence is sometimes also a species of crystallization, such as the beautiful vegetations which shoot up from different saline substances. See Crystalization.