Automatic Crystal Chemical Classification of Silicates Using Direction-Labeled Graphs

In crystallography several classification methods have been proposed to put crystals in an order suitable for specific purposes. The method we consider in this paper [Li1,Li2] has been developed for the classification of silicates in order to characterize the elements of this largest single group of minerals according to crystal chemical properties. The classification mainly refers to structures in the anion part of silicates which result from connections between Si-0 n polyhedra via common oxygen atoms ('oxygen bridges'). Silicates are characterized by the shape of fundamental structures formed by the linked polyhedra and suited to compose their anion part by successive linkage.