Laws of crystallography Crystallography is the branch of science which deals with the geometry, properties and structure of crystals and crystalline substances. It is based on three fundamental laws. The law of constancy of interfacial angles : It states that the size of the faces or even shapes of the crystals of a substance may vary widely with conditions of crystallization yet the interfacial angles between any two corresponding be 90˚ , irrespective of the size and shapes of faces. The measurement of crystal angles is important in the study of crystals. * Interfacial Angles- The crystals are bound by plane faces. The angle between any two faces is called an interfacial angle. It is indicated from the above figure that the shapes of crystals are different but the angle between any two corresponding faces is 90˚. 2. Law of rational indices (Hauy’s law): This law states that “the ratio between the intercepts on the axes for the different faces ...