ABSTRACT
Mining waste at times is reworked. This is the result of improved extraction techniques, particularly in the case of metals, and more favourable economic conditions. For instance, waste tips from the old gold mines around Johannesburg, South Africa, have been reworked for their gold content. The mining of galena in the Pennines of Britain produced notable volumes of waste containing calcite, barite and fluorspar. Some of the spoil heaps subsequently were reworked to extract the barite, which has been used as an additive for drilling fluids in the offshore oil industry; and to extract fluorspar for use in the steel industry. Similarly, many colliery spoil heaps have been reprocessed to extract the coal content that was not removed by earlier, less advanced mineral processing techniques.
