A key for identification of rock forming minerals in thin section The key for identification of rock forming minerals provides an efficient and systematic approach to identifying minerals in thin section. It is structured in the form of a dichotomous key comparable to those widely used in botany and entomology. The present key gives a unique solution for each mineral. The key covers more than 150 of the most commonly encountered rock forming minerals plus a few rarer but noteworthy minerals indicative of particular conditions. Illustrated in full colour with high quality photomicrographs of each mineral it also provides the most comprehensive atlas of rock forming minerals currently available.