Bases of the Treatment of
Gold Minerals

The minerals of gold (natural gold, principally) possess some characteristic properties which have conduced to the development of the methods of treatment of the minerals of gold.

These properties are mainly the following:

• The density of the gold and the minerals which are carriers is, in general, very elevated. This reaches, for example, 13 to 19 in natural gold, according to the proportion in silver.
• This elevated value has lead to the development of the techniques of gravimetric concentrations, known from a long time ago and until the present time.
• The character, naturally hydrophobic of the surface of the natural gold confers to it an excellent floatability.
• If one observes that the gold is frequently associated to the sulphurs easily floatable, it is understood that the flotation will be a method of treatment much used for the elaboration of concentrates.
• Gold and some of its minerals which are carriers are soluble in the diluted solutions and alkaline of cyanide.

This property to the lixiviation of the cyanide, technique of treatment more current for the minerals of gold.

Gold is also soluble in other solvents, those which allow mentioning the thiourea and the thiosulphates in an acid environment. These two compounds could know its industrial growth in the following years.

In all cases, one can note that before the presence of a solvent it is necessary that the solution of attack has a potential of sufficiently elevated oxide-reduction to be able to place the gold in solution (Pourbaix).

The presence of an oxidizing agent is therefore indispensable; it is the oxygen of the air the one which plays this role in the case of the Cyanidation.

The gold is finally dampened by the mercury, due to the fact that the tension of the surface between the gold and the mercury is weak.

This property is used in the amalgamation, known for a long time already, used in centuries past above the more approximate minerals and today above the concentrates of the gold.

The amalgamation is a technique which loses ground progressively, due to the fact that in part it does not allow recuperating the free gold and, in another part, demands a very strict control for the preservation of the surrounding areas.