Cleveland Mining (ASX: CDG) is well on its way towards achieving stable operations at its Premier Joint Venture Project in Brazil after producing greater than 99% gold recoveries from its new In-Line Leach Reactor (ILR) following first round optimisation work.
Notably, the result using the standard flow sheet means further optimisation studies of the unit are not required.
The company also noted the optimal leach residency times of about six hours confirms the ILR's high efficacy in treating Premier material while the relatively low cyanide consumption will sustain low operating costs.
The ILR unit also allows for a detoxification treatment of the processed material, which means that no cyanide is released in the tailings material, while its full automation creates a closed operating circuit that will enhance site security.
"These results confirm our original belief that Premier's mineralisation is highly amenable to a gravity plus ILR recovery process," managing director David Mendelawitz said.
"We will achieve major cost savings, both capex and opex, from the ILR unit as compared to our original thoughts of installing a CIL plant."
The project has been fast-tracked to allow for accelerated installation, operation and gold production. Installation and commissioning is expected to be completed in January/February by members of Gekko's experienced Technical Team.
In-Line Leach Reactor
Cleveland had purchased the ILR unit from Australian supplier Gekko Systems to increase the overall recovery rate from the current level of around 60% up to the targeted level of 75%.
Prior to shipping, Gekko had studied the optimum chemical balance and residency times required to effectively treat ore from Premier, confirming its mineralisation responded positively to the lowest level of cyanide and shortest residency times that were trialled.
Besides the high recovery of +99% and low cyanide use, the ILR's ability to detoxify the processed material is an environmental boon and adds to the appeal of the unit relative to other chemical treatment processes.
The ILR-2000BA model that was purchased by Cleveland can process 5 tonnes of gold concentrate per batch, more than enough to accommodate the targeted ramp up to 30,000 tonnes per month to produce about 60 tonnes of concentrate per month.
Under Cleveland's existing recovery circuit, around 70% - 80% of contained gold within the head feed is recovered through the front end milling and Falcon concentrator process.
Once the material is processed into a concentrate, not all the contained gold within the concentrate can currently be recovered with a gravity table due to similarities in the mass of the fine gold proportion and the associated sulphides.
The ILR unit will improve this recovery by extracting the gold from the concentrate using cyanide, thus negating this issue.
The proven Gekko ILR technology, with over 100 units around the world including 27 in South America, chemically extracts gold from material that previously would have been liberated by the gravity circuit but not captured by the gravity table.
Premier Joint Venture Project
Cleveland had recently revised mine plans for the Metago and Pit 3 gold open pits at its Premier Joint Venture Project that provide further confidence towards achieving stable operations and set a medium-term target of 7,000 gold ounces per quarter from the Metago pit.
Under the plan, the two pits would produce about 19,000 ounces of gold over 20 months through processing of 30,000 tonnes of ore per month, generating an estimated margin of A$12.6 million. This will provide healthy debt servicing cash flow and also finance resource expansion.
While the company's medium-term target of 7,000 gold ounces per quarter will take 15,000tpm from the Metago pit and draw the remaining 15,000tpm from other higher grade sources, AMC's 30,000 tpm Upgraded Case provides confidence that Metago alone can provide 30,000 tpm until the other sources can come online to produce the targeted gold output.
The company also updated its Resource to 950,000 tonnes at 1.52g/t gold, or 46,400 ounces of gold comprising 18,900 ounces at 2.14 g/t of Indicated Resource and 27,500 ounces at 1.29 g/t of Inferred Resource.
Infill and exploration drilling on the down-dip and lateral extension of the mineralization will be conducted during the first stage mining operation, aimed at expanding the open cut mining area resource through the continued conversion of Inferred to Indicated resources, plus the inclusion of new resource tonnages.
The strong +99% gold recoveries from the new In-Line Leach Reactor and confirmation that it will use relatively low cyanide provides greater certainty that Cleveland will achieve its medium-term production target of 7,000 ounces of gold per quarter that yield C1 cash costs of circa A$400 per ounce.
It is now well on the road towards stabilising production and establishing profitability.
Plans are also in place to build its Resource through further drilling and exploration work.
Shares in the company should gain on today's news.
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