Ore dressing
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Ore dressing is one of the principal processes in the work of mining. When the miner hoists his ore to the surface, the contained metal may be either in the native uncombined state, as, for example, native gold, native silver, native copper, or combined with other substances forming minerals of more or less complex composition, as, for example, telluride of gold, sulphide of silver, or sulphide of copper. In both cases the valuable mineral is always associated with minerals of no value. The province of the ore-dresser is to separate the values from the waste, for example, quartz, felspar, or calcite, by mechanical means, obtaining thereby concentrates and tailings. The province of the metallurgist is to extract the pure metal from the concentrates by chemical means, with or without the aid of heat. There are also a number of non-metallic minerals which do not have any value, or at best do not reach their highest value until they have been subjected to some form of mechanical preparation; among them are diamonds, graphite, corundum, garnet, asbestos, and coal.
This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
