New bit of information is that the first BIOX plant in Australia, opened in 1991 at Harbour Lights. The BIOX technique is a bacterial oxidation process to increase gold recovery after conventional extraction with NaCn. Other Australian mines continue using the BIOX process including the Wiluna and Fosterville mines.
"The Harbour Lights BIOX Plant"
The Harbour Lights Mine, near Leonora in Western Australia, mined a refractory orebody, with the gold associated mainly with arsenopyrite and pyrite. Sulphide flotation was used to produce a concentrate containing 80 g/t gold,18% sulphur and 8% arsenic. The concentrate was cyanide leached and the residue, still containing 40 g/t gold, was stockpiled.
The BIOX technology was licensed to Harbour Lights for the treatment of stockpiled and fresh concentrate. A process design package was provided to an Australian engineering company for the construction of a 40 tonne per day plant.
Construction started in June 1991 and commissioning commenced at the end of 1991. Full production was achieved by June 1992. A performance test run conducted in October 1992 demonstrated that the guaranteed gold recovery of 92% could be achieved at the design throughput rate.
The successful operation of the Harbour Lights BIOX plant again confirmed the commercial viability of the technology. BIOX plants are easy to operate (Harbour Lights used one operator per shift), and the bacterial strain can adapt to new environments within a relatively short period. Operations at Harbour Lights were terminated in 1994 when the orebody was depleted. The BIOX plant was decommissioned at the end of that year.
