An Integrated Mineralogical Approach to the Biooxidation of Sulphide-Bearing Refractory Gold Ores

Abstract

The deportment of gold in the biooxidation feed and product, from the Harbour Lights biooxidation plant in Western Australia, was determined using optical microscopy, SIMS (Secondary Ion Mass Spectrometry), TOF-LIMS (Laser Ionization Mass Spectrometry), and EPMA (Electron Probe Microanalysis).

Visible gold, which is enclosed in sulphide minerals, is liberated as the host mineral is dissolved in the bioleaching environment. ‘Invisible’ or submicroscopic gold is either concentrated on the surface of the host sulphide mineral as a submonolayer or could be released into the liquid phase, where at typical operating conditions it is unstable and will adsorb onto the surface of other ore particles with a net negative surface charge. By virtue of its position on the surface of the particles this gold is now rendered readily cyanidable. Zones of gold enrichment in pyrite and arsenopynte particles have been confirmed to be preferred sites for bacterial oxidation.

Keywords:

• Bioleaching
• sulphide minerals
• refractory gold
• Thiobacilius ferrooxidans
• microbeam techniques