There has long been a symbiotic relation between geology and industry. Knowledge obtained by geologists is applied to the needs of the extractive industries who, in turn, provide artificial exposures which are used to further the science. The importance of extractive sites is greatest in the south and east where natural exposures are almost wanting, and least in the north and west where natural rock outcrops abound. For the instructor in charge of a field party, large quarries provide the most suitable and accessible demonstration sites in that they show clear and extensive sections, often in three dimensions. To the research worker, mineral workings of all types and ages supplement the information to be gleaned from the frequently small and obscure, natural outcrops. Recent trends towards centralization in the extractive industries have diminished the benefits mineral workings yield to research. The concentration of mineral production in a few large, highly mechanized centres provides less scientific information per unit of production than the smaller, but more numerous, scattered pits, often handworked, of a century ago. Although friction between mineral operators and geologists is remarkably slight, clashes of interest with geomorphologists are frequent. In limestone country, for instance, caves and pavements are destroyed by mineral workings, while in gravel- and sand-bearing areas many features are liable to bodily removal. For geologists, conservation problems typically arise on extractive sites only when they are worked out; for geomorphologists, on the other hand, they arise in many cases as soon as working starts.