Initial metallurgical test work has returned an average 77.8% and 90.7% silver recovery from grind and two-stage leach across mineralisation at Thomson Resources’ Twin hills and Mt Gunyan deposits in southern Queensland.

Encouraging gold and zinc recovery results were also received from the Texas district Twin Hills, Mt Gunyan and Silver Spur silver gold base metal deposits with results up to 76.9% gold and 92.8% zinc.

Location of the Mt Gunyan, Twin Hills and Silver Spur deposits.
Pic: Thomson Resources

Results hold ‘the key’ to a commercially sustainable project

Thomson Resources (ASX:TMZ) executive chairman David Williams said this is a significant milestone for the company, with the metallurgical outcomes representing the key to not only the Hub and Spoke strategy, but to building a successful, commercially sustainable project.

“Particularly with the Texas projects, there were massive gaps in understanding of how to deal with each of the deposits,” he said.

“This was something not understood well by previous operators of the Texas silver mine.

“We can now see where and why they ran into problems with adopting a heap leach processing system, and how we can achieve a better outcome with a different process and with the potential for significantly higher silver recoveries from the Twin Hills and Mt Gunyan deposits.”

Potential for production of quality zinc-silver

The processing pathways are also starting to become much clearer, Williams said.

“We have to keep reminding ourselves that we have the benefit of many tens, maybe hundreds, of millions of dollars of drilling and other mining information by previous operators, which we can harness.

“Added to this is the first ever test work on Silver Spur (along with Mt Gunyan) and we are seeing the potential for production of good quality zinc-silver concentrate from Silver Spur.”

A sliver of history

The Texas heap leach silver mine was operated by Macmin Silver Ltd (MMN) between 2006 and 2008 and by Alcyone Resources Ltd (AYN) between 2011 and 2013 with all ore stacked during this period mined from the Twin Hills pit.

After the shutdown of the MMN/AYN mining and heap leach operation, Moreton Resources Ltd (MRV) undertook a sampling program and published a mineral resource with a silver resource on the four heap leach pads, before closing the operation in December 2019.

No previous metallurgical studies published for Mt Gunyan

Metallurgical test work carried out by previous operators of the Texas silver mine was focused on the Twin Hills deposit and on the heap leach process for the recovery of silver.

No metallurgical studies were published for the Mt Gunyan silver project, with MRV’s MRE for the Mt Gunyan deposit relying on an assumed 60% silver recovery based on the Twin Hills heap leach metallurgical test work.

On top of this, no metallurgical studies were undertaken by previous operators on the Silver Spur silver-zinc-lead-copper deposit.

Thomson’s work was designed to address the Texas district’s metallurgical knowledge gaps and deliver the final pieces of metallurgical information needed to initiate a process pathway study for the New England Fold Belt Hub and Spoke projects.

Looking ahead

The test work suggests that a hydrometallurgical process such as the grind and 2-stage leach process could recover a portion of the contained copper and zinc for the Twin Hills, Mt Gunyan and Silver Spur oxide – transition mineralisation.

As there is no documented heap leach style test work on the Mt Gunyan deposit, Thomson is carrying out a bottle roll test on coarse (10 mm) composite sample which is currently underway and will provide an indication of the expected metal recoveries in a heap leach operation.

Results are pending and will be reported once available.




This article was developed in collaboration with Thomson Resources, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.