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Silica sand quarry

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Silica sand processing is of varying degrees of complexity, and depends on the nature of the raw material and the end use of the sand. It typically requires a high capital investment in plant. Processing is aimed at improving both the physical and chemical properties of the sand to meet user specifications. Typically several grades of sand are produced from one site either by selective extraction and/or processing. At most operations processing involves washing, attrition scrubbing and size-classification to remove the coarse and very fine fractions and to obtain a clean sand with the desired particle size distribution. Blending of lower and higher quality material is undertaken to optimise the use of the reserves. For the production of colourless glass sand, more sophisticated processing is required to remove contaminating impurities, either from the sand and/or from the surfaces of the individual sand grains. Gravity separation using spiral classifiers are used to remove heavy iron-bearing minerals and chromite. Increasingly, however, high intensity wet magnetic filters are being used to remove iron-bearing impurities, including mica. Hot sulphuric acid leaching is used at Devilla Forest in Scotland, to remove iron oxides coating the individual sand grains. Most foundry sands have to be supplied dried and drying facilities are a substantial capital investment

The extraction and processing of silica sand involves the production of only small amounts of waste. Yields of saleable product are on average about 90%, excluding overburden removal, which is used in site restoration.