The 'Delft' system for mineral identification. Vol. 1. 'Opaque minerals'

University of Technology by the late Professor A.H. van der Veen, about half a century ago, and ever since it has been part of the curriculum for students in mining and mineral engineering. Teaching students to identify minerals by means of reflected-light microscopy has always been a matter of considerable difficulty. However, the introduction of quantitative methods during the past decade has greatly facilitated this task and systematic tables listing reflectance values and micro-hardness data are available. Unfortunately, it has been our experience that beginning students have considerable difficulty in using these tables for a number of reasons. These include the inherent inaccuracies in determining the reflectance and micro-hardness values and the fact that these values show appreciable overlap for different minerals. The present system is based upon mineral identification by means of a number of semi-quantitative measurements and observations that can be obtained readily. The system has been used in the instruction of students for a number of years and has proven to be operabie. Following a course consisting of fifteen instruction periods, each of three hours duration, most students were able to identify any of the 195 'common' minerals listed in these tables. We wish to emphasize however, that our system is not intended to replace the available tables such as Uytenbogaardt and Burke's or those to be published by the COM. On the contrary, it has been our intention to facilitate the use of those tables. Reflected-light microscopy obviously involves more than the use of determinative tables. Tables alone cannot teach the student to observe intelligently, or to operate his instruments properly. Nor do they provide an understanding of the physical significance of the measurements that are being made. This type of information must be supplied partly by the instructor and partly by reference to textbooks such as Galopin and Henry. The notes contained in the present text are not intended to be more than some comments of a general nature