Speciation and quantification of surface gold in carbonaceous matter by TOF‐SIMS: a new approach in characterizing losses during the gold recovery process

An increasing number of low‐grade gold ore deposits are characterized by the presence of gold as solid solution into the mineral matrix of sulphide minerals which is not directly amenable to gold cyanidation. In order to liberate this submicroscopic gold the ore has to be oxidized before being subjected to gold cyanidation and exctraction. This is mainly done by autoclave pressure oxidation (AC POX) or roasting, two major technologies used by the mining industry. Very often, these ores contain an active carbonaceous compound which has the ability to adsorb, or preg‐rob gold from the cyanide solution. Gold recovery can be adversely affected by preg‐robbing on inherent carbonaceous material during autoclave pressure oxidation of sulphide ores. The time of flight (TOF) SIMS (TOF‐SIMS) technique has been applied for direct determination of gold species on individual carbonaceous particulates from AC POX stream samples. The speciation of the gold preg‐robbed on carbonaceous matter from CIL tail sample showed presence of both metallic gold and Au(CN) 2 compound. Direct quantification of the metallic and compound gold provided an estimate for the fraction of gold losses due to preg‐robbing in carbonaceous matter.