Toronto-based Orvana Minerals Corp. (TSE:ORV) announced Thursday an updated resource and reserve estimate for its Don Mario Upper Mineralized Zone (UMZ) copper-gold-silver mine in Bolivia, after changes to its mine plan designed to optimize recoveries.
The company said that it has made what it called "significant" changes to the mining and processing aspects of the operation this year, thus warranting the update.
The updated report, effective October 1, estimates reserves of about 177,000 ounces of gold, 5.6 million ounces of silver, and 120 million pounds of copper - a decline of about 5 per cent, 2 per cent and 11 per cent, respectively, Orvana said.
Total measured and indicated resources stand at almost 5.0 million tonnes, grading 1.31 grams per tonne (g/t) gold, 1.29% copper and 39 g/t silver.
The numbers are after considerations for production through September 30 of this year, as well as the exclusion of certain oxide mineralization whose metals cannot be extracted economically.
The miner said testing of these ores will continue in an effort to seek a viable extraction method. The most significant change in the mine plan, Orvana noted Thursday, is the processing of transition ore by a "flotation-only" process, instead of the "leach-precipitation-flotation" (LPF) process.
The mine plan now consists of 720,000 tonnes per year of flotation-only processing of transition and sulphide ores, and 100,800 tonnes per year of LPF processing of oxide ores through 2017.
The LPF processing of 224,300 tonnes of stockpiled oxide ores will also continue in 2018. Indeed, some oxide resource was not included in the current mine plan, since treatment by flotation only or LPF processing was not economically viable due to the input price deck or other parameters used. These resources will therefore be processed "opportunistically" during the life of the mine, Orvana said.
Likewise, some transition and sulphide resources were also not included, and will be mined and processed over the life of the mine if extraction of the metals is economic.
"This mine plan outlines a path forward that optimizes the UMZ operation," said president and CEO, Bill Williams.
"We will continue to pursue opportunities to improve recoveries as well as seek alternatives to extend production beyond 2018, including exploration in proximal concessions."
During October, production from the mine was about 973,000 pounds of copper, 1,440 ounces of gold, and 76,000 ounces of silver. Total cash costs, on a co-product basis, including all royalties and based on sales, were around $1.80 per pound copper, $910 per ounce gold and $16 per ounce silver.
Last month, production was about 1.06 million pounds of copper, 1,290 ounces of gold, and 62,000 ounces of silver at total cash costs of $2.00 per pound, $980 per ounce, and $22.00 per ounce, respectively.
Despite the flotation-only process being operable during October and November, the LPF process is currently active, and the company said processing will switch over to flotation-only next week and continue in January.
Products made from the LPF process include a copper cement and a talc-rich precious metal concentrate, while the flotation-only process yields a copper concentrate with levels of lead from 8% to as high as 20%, as well as a lead concentrate. All products are currently under contract, Orvana said Thursday.
Orvana Minerals produces gold and copper from multiple mines. Its primary asset is the El Valle-Boinas/Carles gold-copper Mine in northern Spain, but it also owns and operates the Don Mario UMZ mine in Bolivia, and is advancing its Copperwood copper project in Michigan, USA.
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