Radius Gold Reports Excellent Silver Recoveries from Initial Plata Verde Metallurgical Tests
In July 2022 Radius announced an Exclusivity Agreement (the "Agreement") with Minera San Julian, S.A. de C.V. ("Minera San Julian"), a wholly owned subsidiary of Fresnillo plc, for Plata Verde Project in Chihuahua, Mexico. See Radius' news release of July 12, 2022. The Agreement granted Minera San Julian an exclusive right for nine months to carry out evaluation and exploration activities in order to negotiate an option agreement to earn a 70% interest in the project. As part of these activities, Minera San Julian sent mineral samples to Fresnillo plc's Technical Services Group, Mineral Processing Department, in Torreon, Mexico ("TSG"), to conduct metallurgical tests.
Bulk samples (approximately 100kg) were collected from the Mina Mojonera and Mina Real underground workings and sent to TSG for initial investigation into metallurgical characterisation and recoveries of metals (silver lead and copper) by cyanide leaching and flotation.
Work index for grinding (Wi) averaged 8.67 kWh/t, classifying the samples as "soft" for ball milling.
Cyanide leach test work reported average recoveries of 93% for silver.
Flotation studies generate Pb/Cu concentrates with a high grade of silver and good values of lead and copper with recovery of around 85% for silver, 52% for lead and 64% for copper.
Combining flotation + tailings cyanidation results in average overall silver recovery of 97%.
Future work should consider separation of Pb and Cu concentrates to generate commercial concentrates.
Bruce Smith, President & CEO, states: "We are very pleased with the recent progress at Plata Verde. Initial test work highlights the exceptional metallurgical properties at Plata Verde with cyanide leach recoveries averaging 93% for silver and in combination with flotation achieving 97% silver recovery. Geological mapping, sampling, and road construction are on-going in preparation for a drilling program."
Details of metallurgical test work
Table 1. Head grade analysis
*average value obtained by direct assay, by fractions and metallic screen
Galena is the main sulfide, which registered around 0.11% by weight, chalcocite 0.12%, and sphalerite, pyrite, chalcopyrite and arsenopyrite, which totaled around 0.06%, were detected to a lesser extent. As silver species, stromeyerite, argentite and a low proportion of AgHg were detected. Non-sulfur gangue represented 99.6% by weight mainly as baryte, calcite, albite, and quartz.
The work index (Wi) averaged 8.67 kWh/t, classifying the Mina Real and Mina Mojonera samples as "soft" material for ball milling.
Direct cyanidation tests
Bottle roll cyanidation tests evaluated the effect of cyanide concentration and particle size on the recovery of elements of metals. The results indicate that the most significant process variable on silver recovery was particle size. Table 2 summarizes the results of the K80 bottle tests carried out around 75 ?m and a concentration of 2.0 g/L of NaCN, conditions considered as adequate for processing Plata Verde material.
Table 2. Summary bottle roll cyanide tests
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(+) Ag g/t & Cu Zn Fe %
(1)Recovery Ag, % = (head-tails)*100/ head
(2)Recovery Cu, Zn, Fe % = mg in enriched solution*100 / (mg in enriched solution = mg in tails)
Silver recovery averaged 93% and the tailings assayed approximately 23 g/t silver. The dissolution of copper, zinc and iron averaged 74%, 3% and 0.25% respectively. Lime consumption was approximately 0.77 kg/t and NaCN 4.2 kg/t.
Standard flotation tests were conducted for Mina Real and Mina Mojonera samples.
Mina Real: Pb/Cu concentrate reported grades for gold of 0.59 g/t, silver 53.7 kg/t, lead 14.5%, copper 14.3%, iron 3.9% and insoluble 17.9% and recovery of 84%, 66% and 71% for silver, lead and copper respectively. Tail grades were Ag = 65 g/t, Pb = 0.05% and Cu= 0.04%.
Mina Mojonera: Pb/Cu concentrate reported grades for silver 54.2 kg/t, lead 14.3%, copper 14.2%, iron 3.5% and insoluble 30.0% and recovery of 86%, 38% and 56% for silver, lead and copper respectively. Tail grades were Ag = 51 g/t, Pb = 0.13% and Cu= 0.06%.
Pb-Cu flotation & cyanidation of flotation tails
Table 3. Combined metallurgical balance of Pb-Cu flotation and cyanidation of flotation tails
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(1)Solutions: Ag, Zn, Cu, Fe in g/m3
(2)Solids Ag in g/t Pb, Zn, Cu, Fe Insol. In %
Samples from Mina Real and Mojonera averaged a global silver recovery of 97% through the combined flotation + tail cyanidation process.
Further investigations related to the high content of barite in the mineral matrix of the samples, that could affect the flotation process, was also recommended.
Quality Assurance and Quality Control
Reported metallurgical testing was conducted by Fresnillo plc's Technical Services Group, Mineral Processing Department in Torreon, Mexico. Metallurgical testing followed industry standard practices and processes.
Bruce Smith, M.Sc. (Geology), a member of the Australian Institute of Geoscientists, is Radius' Qualified Person as defined by National Instrument 43-101 - Standards of Disclosure for Mineral Projects. Mr. Smith has reviewed and approved the technical information contained in this news release.
Radius has a portfolio of projects located in Mexico, United States and Guatemala which it continues to advance, utilizing partnerships where appropriate in order to retain the Company's strong treasury. At the same time, management is seeking out additional investment and project acquisition opportunities across the globe. Radius is a member of the Gold Group of companies, led by Simon Ridgway.
ON BEHALF OF THE BOARD
President and CEO
Contact: Bruce Smith
200 Burrard Street, Suite 650
Vancouver, BC V6C 3L6
Tel: 604-801-5432; Toll free 1-888-627-9378; Fax: 604-662-8829
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