In this title the most significant optical data pertaining to the common rock-forming minerals are presented in simplified tabular form supplemented by additional charts, tables and plates useful in the determination of specific mineral properties. The tables and other data classify and briefly summarise the optical properties of each of the rock-forming mineral groups and, wherever possible, in a systematic manner. Optical details with immediate visual impact, as well as chemical data, are so presented that mineral species within a group can be readily compared. Discriminatory procedures for the techniques of mineral recognition are also provided. No attempt is made to explain optical theory as the manual is intended as a ready reference work for use in the laboratory. Definitions of mineral properties, supplemented by explanatory charts and comparative photographs of minerals in thin section, are additional aids that can be used in the course of routine microscopic mineralogy and petrography.