Mineralogical Classification
of Gold Minerals

The group of considerations that were previously mentioned: mineralogy, presentation of gold, mineral associations, nature of the gang, physical properties as well as chemical, allows us to have as a result a classification of the gold minerals from the point of view of their treatment. Cyanidation would be therefore, the most commonly used treatment technique; obviously this classification relies in great deal on the difficulty presented by the different types of minerals in the application of this technique. 

Gold minerals in the deposits
These minerals are made up by sands or conglomerates only barely or not consolidated. The gold presents itself with a weak content in the form of natural metal. These minerals have been known since ages ago and have been exploited solely for gravimetry.

Minerals that have exonerable natural gold
This category is made up of the minerals that are non refractory in which the gold presents itself in its native state, not included in sulphides. The sulphides are not very abundant and mainly made up of pyrite. Cyanidation is the technique that is normally utilized for these minerals, along with gravimetry, in order to recover the coarse gold that is eventually present. According to the dimension of the coarse gold and its relative proportion, the gravimetry can be more or less developed or reduced only to a function of a trap. Direct amalgamation of the mineral that comes about and which is something that has been done in the past, is no longer done these days.

Minerals with iron sulphides
Gold generally presents itself in these minerals at the same time disseminated in the sulphides and in its free state. Certain sulphides dissolve in the attack solution consuming the reagents and inhibiting the dissolving of the gold. A ventilation in the presence of cal, up towards cyanidation is the treatment that is generally practiced in these cases. Pyrite is the most frequent sulphide in this mineral category. The normal treatment consists in a flotation of sulphides and free gold, followed by cyanidation of the eventually grinded concentrate. Having it previously burned allows the gold to be liberated when it is disseminated in submicroscopic inclusions in the pyrite.

Minerals with arsenic or antimony sulphides
Generally, gold presents itself fin these minerals very finely disseminated in the sulphides. Arsenic and antimony produce more of those refractory minerals to direct cyanidation: the treatment therefore consists in a concentration of the gold by flotation following by the burning and of a cyanidation of the concentrate.

Minerals with gold telluride
These minerals have a part of gold in the form of telluride. These are often times accompanied by natural gold and disseminated gold in the sulphides. The treatment of this mineral is more complex then the previous ones. It can typically withstand flotation of the sulphides followed by cyanidation, a burning of the residues and a re-cyanidation of the calcine. The flotation residues are also eventually followed by cyanidation again.

Minerals with carbonaceous gangue
These minerals contain carbonaceous matter under an organic or mineral form. This carbon can reciprocate the dissolved gold that then becomes lost amongst the residues. The treatment of such minerals requires before the cyanidation a stage of oxidation of the mineral, a separation by flotation of the carbon or the adding of reagents, such as kerosene, recovering the surface of the carbonized minerals.