Routine Preparation of Potished Thin-sections

The colour plate which appears in this number of the Canadian Mineralogist iliustrates the advantage of microscopic observation of mineralized rocks in polished thin-section by incident and transmitted cross-polarized light simultaneously: the identities and relationships of opuqrr" and translucent minerals in contact are immediately evident. The principle is not ne.w; more than a hundred years ago sorby ground rock chips smooth and thin enough to see through; and dozens of publications have since recounted a variety of more or less successful techniques for polished thin-section preparation and examination. Cameron (1961) gives an excellent summary and bibliography of the more recent efforts in his authoritative work "Ore Microscopy." One characteristic is common to all: the methods require skilled hand craft of a high order. Further, microscopes equipped for the simultaneous illumination conditions necessary to take full advantage of the sections, while not particularly complicated or expensive, are not generally available. These real disadvantages have hindered the development and