General Scheme of Mineral Treatment

The conjunctive of considerations which preceed, mineralogy, properties of gold and particularities of the different techniques of treatment allow to define a general scheme of treatment which is found in the most part of the exploitations of gold.

After the preparation of gross gold for gravimetry, an alternative is presented: flotation followed eventually of a cyanidation of all which arrive.

The auriferous solutions are immediately treated to recuperate the gold. The concentrates can be amalgamated, cyanidated or sent directly to the melting of metals.

It is well understood, in the case of a cyanidation in pile, that no gravimetric separation nor pre-treatment are applicable. 

Methods of Gold Recuperation
Once it is extracted, the gold must be recuperated by treatment of the solutions. Two processes are presently used:

The precipitation above zinc or above aluminum, the old procedure; and the absorption of gold above active carbon, procedure apeared industrially in the last decennial.

The amalgamation which is a method of recuperation of gold of the gravimetric concentrates or of flotation has been treated previously.

Precipitation above Zinc or Aluminum
The focus of the precipitation of gold above the dust of zinc as an effective method of recuperation of gold in a cyanide solution has been an important factor for the development and the success of the cyanidation at the beginnings of the last century.

The chemistry of the precipitation is described in Adamson.

The complete process comprehends:

• A liquid/solid separation after the cyanidation (decantation against currents or filtering).
• A clarifying of the auriferous solution.
• A de-aeration of the solution to work under partial emptiness.
• The increase of dust of zinc and salt of lead which betters the precipitation of gold.
• The recuperation of the precipitated gold on a filter, generally pre-covered.

A certain number of elements, particularly copper, can perturb the reaction, so much as from the cynetic point of viewas of efficiency.

The liquid/solid separations and the clarifying are operations sometimes difficult to conduct and expensive for certain minerals (pulp of the mineral finely grinded, clayish mineral).