Practical determination of perfect habits of crystals*

A general scheme for the determination of theoretical habits of crystals on the basis of the works of Wulff and Delone is provided. Satisfactory agreement between the habits determined theoretically and the observed habits is demonstrated for crystals of high temperature anhydrous borates of diverse structure, composition and symmetry. The part played by large cations in forming crystal faces is discussed. For a large group of isostructural crystals of binary borates of trivalent elements an analysis is made of the agreement between the theoretical habits and the real forms, depending on the type of the cation.