Quarrying and ORE-Dressing, which may be considered as branches of mining, are also discussed in separate articles.
The difficulty in separating zinc blende from iron pyrites is well known, and probably the most elaborate ore-dressing works ever built have been designed with this end in view.
In mining it is applied to various machines used in breaking and crushing the ore (see ORE-Dressing) .
In practice, however, we never have to deal with pure zinc minerals, but with complex mixtures, which must first of all be subjected to mechanical operations, to remove at least part of the gangue, and if possible also of the heavy metallic impurities (see ORE-Dressing).
The dressing or mechanical preparation of vein stuff containing gold is generally similar to that of other ores (see ORE-Dressing), except that the precious metal should be removed from the waste substances as quickly as possible, even although other minerals of value that are subsequently recovered may be present.