Operation Techniques &
 Design Factors

The operational techniques selected for a determined installation will depend fundamentally of the characteristics of the mineral, size of the operation and means available, in the way that they can be considered specific for each case. Nevertheless, these techniques include some factors of common applicability.

Floor Preparation
The cyanidation in heap leaching is taken into effect with deposited material over an impermeable base or floor where the sollutions are collected, thus eliminating the possibility of losses of gold and silver, and of contamination of local currents with cyanide. The materials used in its construction include asphalt, concrete, plastic laminas, compacted debris with bentonite and clays, which are chosen according to technical factors (tonnelage and height of the heap leaching, duration of the cycle of lixiviation, etc.), certain local factors also being able to influence them (availability of spacem of materials, etc.) and economicals.

Mineral Preparation
The minerals which are not very permeable to the solutions must be crushed to better the exposition of the values contained at the chemical attack. The optimal degree of crushing is determined through the tests of laboratory in columns, generally justifying a fine crushing with the objective of incrementing the extractions and shortening the period of lixiviation.

The laboratory tests also reveal the necessary amount of lime which must be added to the mineral to neutralize the action of constituents which are formers of the acid, being habitually dossified in dry during the crushing.

Some excessive contained clay minerals or of fine material generated during the crushing are difficult in being treated, due to the problems of porosity and permeability of the bed caused by the segregation of fine particles. In such cases one can apply an aglomeration with the intent of producing a uniform and permanent distribution of such particles, contemplating the formation of firm aglomerates and, at the same time, permeable to the solution. Among various aglomerate agents studied, the best result have been obtained with lime and with cement optimal conditions of 5 kilos of lime or of cement by TM of mineral and 8% to 12% of humidity.