gold recovery, page-19

Gold in pyrite is often dissolved throughout the crystal and its size is effectively the atomic scale. It is released only through the destruction of the crystal lattice either by chemical dissolution or by roasting.

For the Intec gold process to be effective, there needs to be some arsenic present in the lattice to facilitate chemical dissolution. Apparently the pyrite from Hellyer tailings may be deficient in arsenic although I haven't read this in their literature.

This leaves the roasting as the remaining option for gold recovery at Hellyer. Roasting is not part of the Intec gold process as such but for the Hellyer plant it is being considered as a way to provide on site generated sulfuric acid at low cost. The ann of May 2 2008 titled, "Intec Metals Recycling Project Update – Acceleration of Stage 2", contains the following projections, "...liberation of ~8,400 tpa of lead, ~2,800 tpa zinc, ~360,000 oz pa silver and ~4,500 oz pa gold from the Intermediate Lead Concentrate, generating approximately an additional A$42 million per annum in Stage 2 revenues at current metal prices."

It seems then, that the recovery of gold is being considered at Hellyer, not directly through the typical Intec process but through a modification designed primarily to supply low cost sulfuric acid. It's what I would call an elegant solution.