Influences of the accompanying minerals and nature of the gang about the treatment of gold minerals

In man of the own characteristics of gold, certain minerals present in the mineral: sulphides, oxides, gang minerals that have an important influence in the establishing of a treatment process and in the values of the parameters of their function. The knowledge of mineralogy of the gold minerals is therefore indispensable, particularly in the case when the habitual base techniques do not prove to bring about satisfactory results.

Copper, lead and zinc minerals
It has been demonstrated that most of the minerals that have these elements were more or less soluble in the cyanide solutions. The dissolution of these minerals carries an excess usage of cyanide. A mole performance has been indicated, copper over cyanide of 4, needs to be maintained in the solution in order to conserve its dissolving power in face of the gold. Pretreatment towards the top of the cyanidation will often times be necessary in order to palliate this inconvenience. In the case where the base metals are extracted by the same mineral, the gold is often times recovered after the pyrometallurgical treatments of the concentrates of those metals.

Arsenic and antimony minerals
These minerals are more or less soluble in the cyanide solutions, increasing in this way, increasing in this way the absorption of reagents and oxygen. But besides this, this dissolution has by effect to make the kinetic of extraction of the gold slower and of restoring the partially refractory to the cyanidation mineral. This inhibition finds its origin not only in the depletion of oxygen of the solution, but mainly in the formation of a layer in the surface of the pebbles of gold, resulting in the precipitation of the attack products of arsenic and antimony. Another inconvenience of the presence of arsenic in the solutions can be seen with the precipitation of gold on zinc powder. One part of the arsenic can be found in the cement, but above all a formation of AsH3 forms, which is a very toxic gas that requires of careful ventilation of the installation. In the presence of arsenic or antimony, the gold is in general concentrated by flotation and the concentrate is burned. The burning allows it on one side to free the gold up to the cyanidation and on the other, eliminate the arsenic and one big part of the antimony. Careful control of the temperature and the airing of the oven need to be maintained especially in the presence of antimony to avoid the partial fusion of this metal that can then recover the gold particles.