Ores that are mined from the earth are usually contaminated with large amount of impurities such as soil and sand etc.

Concentration or Dressing means, simply getting rid of as much of the unwanted rocky material as possible from the ore. The impurities like sand and clay are called gangue. Here, we should get as for as possible pure or more concentrated ore.

Enrichment (concentration) of the ore: Various physical methods are used to enrich the ore. In many cases, it is possible to separate the metal compound from unwanted rocky material by physical means. An example for this is froth flotation.

The physical methods adopted in dressing of the ore (or) enriching of the ore depends upon difference between physical properties of ore and gangue.