At the March Technical Session held by the AusIMM Melbourne Branch I was fortunate to hear about developments in Rex Minerals’ (ASX:RXM) Hillside Cu-Au Project from their Chief Geologist, Patrick Say.
The Hillside Cu-Au Project, located within striking distance of Adelaide in South Australia was discovered in 2008-2009 and since then a Resource of 330Mt @ 0.8% Cu(eq) has been defined and 120Mt @0.77% Cu(eq) converted into Reserves. Rex Minerals completed a pre-feasibility study in October 2012 and are progressing with development of a 15Mtpa processing facility to produce a proposed 70,000 tonnes of Cu and 50,000oz of gold, along with a sweetener of 1.2Mtpa of magnetite. This will all be done for a C1 cash operating cost of US$1.2/lb Cu (Eq), which is very impressive.
The presentation given by Patrick Say gave an excellent overview of the geology in the Hillside Project. The initial targets had been gravity anomalies associated with IOCG type deposits but drill intersections were found with magnetite and the emphasis was shifted to magnetics. This was a great example of flexibility in geological interpretation and led directly to the discovery of what has turned out to be the largest undeveloped Cu resource in Australia.
From a process mineralogy perspective the project has great potential. Copper appears to be present predominantly as chalcopyrite, although evidence was mentioned of primary bornite+chalcocite enclosing the chalcopyrite-rich core. A small component of the resource is present as Cu oxides and Rex is investigating the potential to recover these zones. This would suggest that potential should exist for an increase on the current Cu recovery of 88% through optimisation of the locking/liberation characteristics.
The gold deportment appears to be fairly typical, with all gold grains located to date associated with Cu sulphide minerals and therefore reporting to the Cu concentrate. This could be expected for the type of mineralisation and there is likely the opportunity to further increase the recovery of gold through use of some statistically detailed gold deportment studies.
Overall, it was great to see a major project being developed in Australia by a junior company. It was pleasing to see that through innovative thinking and smart geology, a project of this size could be discovered within such a close proximity of Adelaide. The development process has been rapid and to move a project of this size from discovery to feasibility assessment within 5 years is a great example of what can happen if a small nimble company is allowed to pursue the development of an opportunity.
The views expressed in this article are the personal views of Dr Will Goodall and have not been made to advertise or promote any particular stock or investment service, but merely to inform. Any factual information on the Blog has been researched by Dr Will Goodall and is taken to be correct and accurate at the time of writing. However, Process Mineralogy Today does not guarantee the accuracy of any factual information contained in the Blog – if you rely on this information in any way; you should cross reference it with other sources.