Chemical Used in Gold Mining - "Refractory Gold ore"

The gold also occurs as sub microscopic particles in sulphides or as absorbed gold onto surfaces of carbonaceous matter. Because of the variation of these refractory ores, gold occurrence is ore specific and before process decisions are made, competent mineralogical and metallurgical evaluation must be carried before final process decisions are arrived at.

Refractory gold ores are generally recovered using more complex pre-treatment processes and reagents. These generally yield very low recoveries if subjected to conventional treatment routes and comprehensive mineralogical and metallurgical test work must be carried out before final process routes are adopted

Refractory gold ores and concentrates are characterized by low gold recoveries and high cyanide consumptions when subjected to direct cyanide leaching. Therefore an oxidation pre-treatment step is required before cyanidation that will break up the sulphide lattice and render gold particles accessible to cyanide ions. The iron sulphide minerals generally need to be activated with copper sulphate before a specialty collector or xanthate (PAX- Potassium Amyl Xanthate) addition (but in some instances this may not be required) The main options for the treatment of refractory ores and concentrates, include a combination of the traditional oxidation roasting, the modern pressure oxidation, flotation, bacterial oxidation and cyanidation. During flotation of refractory ore a Xanthate based collector, Dithiophosphate collector or a combination of these is used. Lime or Sodium hydroxide (NaOH) are also used as pH modifiers depending on the ore characteristics. Copper sulphate is also used as an activator. Frother selection is also critical and ore specific. The final reagent scheme adopted is, however, ore specific based on the grade and varies from place to place.