Treatment Basis for Gold Minerals

Gold minerals (mainly gold) has some characteristic properties that have lead to the development of the methods of treatment of gold minerals. These properties are mainly the following:

• The density of gold and bearers of minerals is, in general, very high. This reaches for example 13 to 19 in natural gold according to the proportion in silver. This elevated value has conduced to the development of techniques of gravimetric concentration, known since a long time ago and until now.
• The naturally hydrophobic character of the surface of natural gold gives it excellent floatability. If one were to observe that gold is often times associated with sulphides, that easily float, it is easy to understand that flotation is a type of treatment that is much utilized for the elaboration of concentrates.
• Gold and some of the minerals it bears are soluble in diluted solutions and cyanide alkalines. This property to the lixiviation of cyanide is one of the most common techniques of treatment for gold minerals. Gold is also soluble in other solvents, which give way to cite thiourea and thiosulphates in an acidy environment. In all the cases, it can be noted that in the presence of a solvent it is necessary that the attack solution has a potential of oxide reduction sufficiently elevated to be able to put the gold in the solution. The presence of an oxidizing agent is therefore indispensable; it is the oxygen of the air that plays the role in the case of cyanidation. Gold is in the end dampened by the mercury, since the tension of the surface between the gold and mercury is weak. This property is used in amalgamation known since a long time ago, used in past centuries on minerals and on gold concentrates. Amalgamation is a technique that is not utilized as much anymore because on one hand it does not allow the recovery of free gold and on the hand; it demands a very strict control of the environment and safety of those working around it.