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Artemis test work supports 93% recovery at Blackwater

2020-12-07 09:25 ET - News Release

Mr. Steven Dean reports


Artemis Gold Inc. has released key findings from continuing metallurgical test work conducted that further support the upcoming definitive feasibility study for the company's Blackwater gold project in central British Columbia, Canada. This latest campaign of test work continues to support the 93-per-cent life-of-mine gold recovery that was applied in the recently completed prefeasibility study dated Aug. 26, 2020, entitled "Blackwater Gold Project British Columbia NI 43-101 Technical Report on Pre-Feasibility Study," filed on SEDAR by Artemis on Sept. 18, 2020.

In the PFS, various recommendations were made for complementary metallurgical test work to support the DFS due for release in mid-2021. The PFS was largely based on a comprehensive, integrated metallurgical test work program carried out by the previous owner of the Blackwater project during 2019. To support the DFS, Artemis initiated a follow-up test work program with Base Metallurgical Laboratories Ltd. in September, 2020, to further examine and optimize process parameters.

Leach extraction

The 2019 test work, utilizing composite samples representing the first five years of mining, were used to further optimize the process parameters. In all, approximately 32 tests were carried out establishing optimal leach duration and recovery at a grind size of 150 micrometres. Combined with gravity concentration, it was shown that, at the optimized conditions, leach plus gravity recovery of greater than 93 per cent could be obtained, with average recovery being 94.6 per cent. As a result, the flow sheet designed for the PFS included a gravity concentrate plant to treat a significant percentage of the ball mill discharge and an extended leach residence time with a preaeration step and CIP circuit.

An additional 48 samples from throughout the deposit were also tested to investigate recovery variability using the standard PFS flow sheet (gravity concentration plus gravity tailings leaching for 48 hours). The average value for gold recovery was 92.6 per cent with the average recovery adversely impacted by six samples. Excluding these six samples, the average recovery of the remaining 42 samples was 94.9 per cent.

To further analyze these anomalies, five of these samples had sufficient material to be retested using the same gravity concentration followed by an extended 48-hour leach (consistent with the PFS operating assumptions), and a higher initial cyanide concentration was used in some cases with lead nitrate added to three of the tests (as this can increase leach recovery). Under these conditions, three of the samples showed significantly increased recoveries and two remained essentially the same. Using the results of the repeat tests added to the 43 other tests gave an overall recovery for the 48 samples of 93.1 per cent, therefore confirming the LOM recovery rate of 93 per cent in the PFS. Automatic cyanide control will ensure adequate cyanide is maintained in operation to ensure optimal recoveries.

Cyanide consumption

The cyanide consumption recorded in the 2019 process optimization test work returned higher cyanide consumption than anticipated. Upon review by Artemis, the test method used did not allow precise control of pH and in many cases pH values of less than 10.5 were recorded during the course of the leach tests. At a pH level below 10.5, cyanide can be lost due to the associated volatilization (evaporation) of HCN.

Tests carried out on the one remaining composite sample, with a focus on pH control, resulted in cyanide consumption of 0.59 kilogram per tonne with a gold recovery of 94.5 per cent gold and 60.2 per cent silver. This is consistent with the 0.6 kg/t cyanide consumption used in the PFS.

Recovery rates for low-grade ore

Large composites of low-grade (less than 0.4 gram per tonne) materials are being treated through the standard flow sheet to confirm the recoveries to be expected from low-grade ore, which is planned to be stockpiled and processed in phase 4 at the end of the mine life. Tests on lower-grade samples so far have exhibited recoveries in excess of 93 per cent.

Steven Dean, chairman and chief executive officer, commented: "We are pleased to see that the additional metallurgical test work completed to date further supports a plus 93 per cent gold recovery for Blackwater, consistent with the gold recovery applied in the PFS. We were particularly pleased that the results demonstrate a limited relationship between grade and recovery, with an approximately 92.7-per-cent average recovery for one g/t samples. These results support the proposed design for the process plant at Blackwater as reported. Detailed engineering work is ongoing with the results to be incorporated into the DFS for Blackwater, which remains on track to be completed in mid-2021."

Technical disclosure

All metallurgical test work referenced in this press release has been completed by Base Metallurgical Laboratories Ltd., based in Kamloops, B.C., Canada.

Data verification consisted of ensuring that the samples selected came from within the area where mineral reserves were estimated and that the selected samples were representative of the ore to be mined. The qualified person checked that the sampling protocol used was applicable for the planned test work. In the QP's opinion, the test work conducted was completed by a reputable metallurgical testing facility and used industry-standard methods. The QP has visited the test work facility.

Qualified persons

John A. Thomas, PEng (JAT Met Consulting), independent of the company and a qualified person as defined by National Instrument 43-101, has reviewed and approved the scientific and technical information in this news release.

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