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Discovery Silver Corp
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Discovery Ag Cordero met tests recover up to 89% Ag

2021-09-07 11:51 ET - News Release

Mr. Taj Singh reports


Discovery Silver Corp. has released results from its metallurgical test program on representative samples from the Cordero deposit. This program represents the most comprehensive test work completed on Cordero to date. Tests were completed at the Blue Coast Research Ltd. laboratory located in Parksville, B.C., Canada. Highlights from the test work include:

Sulphide flotation test work

  • Silver recoveries of 80 to 89 per cent, lead recoveries of 83 to 91 per cent and zinc recoveries of 81 to 90 per cent from locked cycle tests;
  • Test work completed on all major rock types at Cordero;
  • Higher recoveries were achieved at coarser grind sizes;
  • Saleable concentrate grades confirmed and levels of penalty elements for concentrates were insignificant.

Oxide and transition cyanidation test work

  • Silver recoveries of 54 to 80 per cent and gold recoveries of 61 to 75 per cent at coarse crush/grind sizes from coarse bottle roll testing;
  • Results represent the first indication that a heap leach on the oxide and transition material at Cordero may be economic;
  • Follow-up column leach test work is currently under way.

Taj Singh, president and chief executive officer, states: "The results from this metallurgical test work program represent a major de-risking step for Cordero. All major rock types hosting sulphide ore returned excellent recoveries via conventional flotation processes to generate clean, highly saleable concentrates.

"In addition, there were two new positive developments that also emerged from the test work. Firstly, the highest recoveries were achieved at coarse grind sizes of 175 to 200 microns, which should help reduce capital and operating costs for the project. Secondly, mineralized oxide and mixed oxide-sulphide (transition) 'prestrip' material that sits at surface above the large sulphide ore body responded very well to cyanidation introducing the potential to heap leach this material at the start of the mine life. Both developments should have a positive impact on the overall project economics that will be outlined in our preliminary economic assessment due for release next quarter."

Sulphide flotation:

Differential lead-zinc flotation test work was completed on medium-grade sulphide samples representing the four different rock types at Cordero. Samples were sourced from across the deposit in both the North and South corridor. Test work confirmed excellent recoveries for silver, lead and zinc via conventional flotation processes to generate separate lead and zinc concentrates. Saleable concentrate grades were achieved and levels of penalty elements for both concentrates were insignificant. Significantly, close to 90 per cent of the recovered silver reports to the lead concentrate where the highest payabilities are applicable.

Sample selection:

  • Samples of the four major rock types were sourced from locations spatially throughout the entire deposit including the Pozo de Plata and northeast extension zones in the North corridor and from along the central and southwest parts of the South corridor;
  • Given the low variability in the rougher test results based on sample location master composites were created based on the four rock types for cleaner and locked cycle tests.


  • Bond abrasion index (Ai) ranged from 0.142 to 0.351 gram for each rock type; this corresponds to a categorization of slightly abrasive to medium;
  • Bond ball work index (BWI) ranged from 17.6 to 19.5 kilowatt hours per tonne (metric); this corresponds to a categorization of hard ore;
  • Higher recoveries were achieved at coarser grind sizes; a targeted coarse grind size of 80 per cent passing 175 to 200 microns will be assumed for process design purposes.

Locked cycle tests:

  • Locked cycle tests were completed on each of the four major rock types at a targeted grind size of 200 microns;
  • Excellent recoveries were achieved for silver (80 to 89 per cent), lead (83 to 91 per cent) and zinc (81 to 90 per cent);
  • Close to 90 per cent of silver reports to the lead concentrate -- this is highly significant to the potential economics of an operation at Cordero, as the highest silver payability is received for silver in the lead concentrate;
  • Low recoveries for gold were in line with previous test work; the majority of gold is associated with pyrite that gets rejected during the concentrate cleaning process.

Concentrate analysis:

  • Saleable concentrate grades for both lead and zinc concentrates were readily achieved as highlighted;
  • Level of penalty elements was low, confirming excellent saleability of both concentrates as outlined .

Planned additional test work:

  • Testing of low-grade sulphide material representative of potential stockpile material recently commenced and is continuing; results are expected to be incorporated in the upcoming PEA of the Cordero project scheduled for completion in Q4 2021.

Testwork on oxide/transition:

Cyanidation test work was completed on the oxide and mixed oxide-sulphide material at Cordero. The oxide and transition material in aggregate represents approximately 5 to 10 per cent of the total ore body. Test work consisted of coarse bottle roll test work at different crush/grind sizes. Based on the excellent results from these initial tests, column leach test work commenced in July, 2021, with McClelland Laboratories Inc. based in Reno, Nev. This will be the first column leach test work conducted on oxide and transition material and if successful, it offers the potential that a commercial heap leach operation could be included in the processing plan in the early years of the project life. Such a heap leach operation would recover silver and gold from "prestrip" material that would typically be regarded as waste rock. Preliminary results from the column leach test work are expected to be received in Q4 2021, in time to be included in the upcoming PEA.

Coarse bottle roll tests:

  • Oxide and transition samples were selected from widespread locations in both the North and South corridors. The level of oxidation in the transition samples varied from 20 per cent to 80 per cent;
  • Tests were completed at different crush/grind sizes on both oxide and transition material;
  • Results confirmed the potential for oxide/transition material to be recovered via heap leach processing.

Planned test work:

  • Agglomeration, load-permeability and column leach test work has recently commenced with McClelland;
  • If results from this test work are positive, a commercial heap leach operation will be included in the upcoming PEA.

About Discovery Silver Corp.

Discovery's flagship project is its 100-per-cent-owned Cordero project, one of the few silver projects globally that offers margin, size and scaleability. Cordero is located close to infrastructure in a prolific mining belt in Chihuahua state, Mexico, and is supported by an industry leading balance sheet with over $80-million available for aggressive exploration, resource expansion and future development. Discovery was a recipient of the 2020 TSX Venture 50 award and the 2021 OTCQX Best 50 award.

About Ausenco

Ausenco is a global diversified engineering, construction and project management company providing consulting, project delivery and asset management solutions to the resources, energy and infrastructure sectors. Ausenco's experience in gold projects ranges from conceptual, prefeasibility and feasibility studies for new project developments to project execution with engineering, procurement and construction, and engineer-procure-construct delivery.

About Blue Coast Research Ltd.

Blue Coast, founded in 2009, owns and operates a 12,000-square-foot laboratory in Parksville, B.C., Canada, and has a team of minerals engineers, scientists and technicians with experience that spans decades. Blue Coast provides high-quality metallurgical testing, analytical services, flowsheet development, consulting and operational support and are a well-known and trusted partner in the global minerals industry.

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