Calcium sulphate dihydrate nanocrystals of 25-100 nm width have been synthesized in 100% purity and yield by means of a method-the cryo-vacuum process-consisting of rapid freezing of quasi-saturated solutions and subsequent vacuum assisted sublimation of water. Transmission electron microscopy reveals both curled nano-lamellae and smaller, irregular particles; electron diffraction patterns demonstrated that the particles are crystalline. This is a very powerful method for the 'clean' synthesis of moderately and completely water-soluble inorganic materials. (c) 2005 Elsevier Inc. All rights reserved.