A gold mine is a desirable asset, representing wealth and success. For the prospectors of gold, the lure of shiny yellow metal in streams promised richness; however, barring a few rare examples, gold is no longer so easily acquired. Gold today more commonly occurs in complex metal sulphide ores that require mineral separation and chemical or thermal treatment to render the metal amenable to collection and concentration. Along the way, it must be separated from its metal neighbours. Due to a change in the world´s focus on metals, many of these neighbours are now considered valuable, some even more than gold itself. Understanding the geometallurgy of a gold ore is essential in discerning wanted from unwanted neighbours.
Gold is associated with pyrite in almost all ore types. Pyrite may encompass more chemicals than its parts of iron and sulphur. Indeed, gold itself can be part of the pyrite if sufficient arsenic is present, such as in the Carlin belt of Nevada. Here, arsenian pyrite is the main gold mineral, and separation requires intense processing and waste management. Due to the presence of mercury, even atmospheric discharges need treatment. To quote the motto “forewarned is forearmed,” understanding this can improve process design to ensure gold’s neighbours do not poison the product or the environment.
Another motto, “all that glitters is not gold,” can be inversed: not all gold glitters. Gold forms chemical compounds not only as a trace of sulphides, but also as rare minerals containing critical metals such as tellurium, selenium, antimony, and bismuth. Identifying such minerals allows the metallurgist to collect these forgotten metals, produce a value critical need and benefit from an unexpected bounty. Once again, good mineralogical knowledge and geological insight into a deposit improve geometallurgical knowledge and allow the benefit of a gold ore to be maximised.
