The science of Crystallography has for its object the classification of crystalline forms.

The principles which must guide us in attempting to arrive at a natural classification of crystals are the same as those which have been so successfully applied to the formation of a natural classification of plants by Ray and Jussieu, and of animals by Cuvier.

By the application of these principles it has been found that crystals are formed on six different types or plans of structure, and in consequence crystals have been arranged in six primary classes, termed crystallographic systems. They are named the cubic, pyramidal, rhombohedral, prismatic, oblique, and anorthic systems.