Banyan Gold Announces Positive Metallurgical Test Results, AurMac Project, Mayo, Yukon

VANCOUVER, BC / ACCESSWIRE / February 6, 2024 / Banyan Gold Corp. (the "Company" or "Banyan") (TSXV:BYN)(OTCQB:BYAGF) is pleased to announce positive results from the Phase 1 metallurgical test program conducted on the Company's AurMac Project in the Yukon Territory. Phase 1 metallurgical testing focused on the AurMac Project's Powerline Deposit ("Powerline") as Powerline hosts the majority of the Project's 6.2 million ounce ("Moz") gold inferred Mineral Resource Estimate ("MRE"). Results from the metallurgical test program demonstrate robust recoveries throughout Powerline, identifying multiple conventional mineral processing flow sheets which the Company continues to advance and optimize through ongoing metallurgical test work.

Highlights :

• Gold recoveries averaged 91% from 75 micron ("um") (200 Mesh) bottle roll cyanidation tests.
• Gold recoveries estimated to be 91% for the Carbon in Leach ("CIL")/Carbon in Pulp ("CIP") process.
• Gold recoveries for the combined gravity and flotation process are estimated at 84%.
• Heap leach gold recovery is estimated to range from 64-72% based on coarse size (9.5 mm) bottle roll testing, conventional column leach tests and Vat leach diffusion extraction testing.
• Flotation recovery into a rougher concentrate recovered on average 89% of the gold with a low mass pull of 3.7%, indicative that a small percentage of material would require further processing.
• Low cyanide consumption at an average of 0.52 kg/mt for primary grind of P₈₀ passing 75 um.
• Gravity recovery has shown it may be an effective part of the flow sheet.
• Low sulphide concentration and excess buffering capacity indicates Powerline is non-acid generating.

"Metallurgical test work highlights robust gold recoveries with multiple conventional mineral processing flow sheets and further optimization has a high likelihood to result in increased overall gold recoveries," Tara Christie, President & CEO, stated. "These results represent a significant step forward at AurMac and continued work will focus on crush and grind sizes, in addition to power and reagent consumption. Work will be focused to support a future economic study using one or more of the identified processes."

Potential Mineral Processing Flow Sheets

Three gold recovery process flow sheets have been identified through the Phase 1 test program. This includes CIL or CIP gold extraction processes (91% gold recovery). The CIL/CIP flow sheet is the most commonly used milling gold recovery method worldwide. Canadian examples include Agnico Eagle's Detour Lake and Malartic Mines in Ontario and Quebec, respectively. The second process is conventional mill flotation (84% gold recovery) which is used at Kinross Gold's Paracatu Mine in Brazil and Centamin's Sukari Mine in Egypt. Test work supportive of gravity recoverable gold was also carried out that indicates a gravity recovery circuit could be included in either the CIL/CIP or mill flotation flow sheets to enhance gold recoveries and reduce reagent consumption. The third flow sheet is heap leach processing (64-72% gold recovery), a commonly used method for high volume, low-grade gold deposits; examples include Victoria Gold's nearby Eagle Mine in the Yukon and Kinross Gold's Fort Knox Mine in Alaska. Mines such as Fort Knox utilize both heap leaching and conventional mill processing.

Methodology

The Phase 1 metallurgical test program focused on the Powerline Deposit as it represents the majority (~62%) of the AurMac Project's current 6.2 Moz gold inferred MRE. Banyan submitted 34 individual intervals (~991 kg) of representative drill core from Powerline to Forte Analytical in Fort Collins, Colorado. The individual intervals selected were based on gold grade, depth from surface, spatial distribution, and lithology. Three master composite samples were prepared from the individual sample intervals as shown in Figure 1 and the composites were based on the three dominant lithologies identified within Powerline which include, Comp 1 - calcareous schist ("CSCH"), Comp 2 - muscovite quartz schist ("MQST") and Comp 3 - sericite schist ("SSCH").

The Phase 1 test program for Powerline included acid-base accounting, mineralogy, comminution, bottle roll cyanidation (9.5 mm and 75 um), flotation, gravity recovery, column leach tests, Vat leach diffusion extraction tests, and a gravity-flotation-intensive cyanidation process simulation. The program was overseen by Deepak Malhotra (SME-RM of Forte Analytical) who is a Qualified Person as defined by National Instrument 43-101, Standards of Disclosure for Mineral Projects ("NI 43-101").

Figure 1. Metallurgical Sample Locations from the Powerline Deposit

Sample Assays and 75um Bottle Roll Testing

Head samples were assayed by both fire assay and metallic screen fire assay ("MSFA") (Table 1) with fire assays averaging 0.76 g/t gold for the test intervals and an overall average of 0.66 g/t gold for metallic screen fire assays. Calculated head assays based on the bottle roll tests is shown in Table 1. The variability in the head assays, calculated head grade assays and MSFAs demonstrate the known nuggetty coarse gold exhibited in Powerline. The total sulphur in the samples ranged from 0.39% to 1.15% with an average of 0.70%, and total carbon ranged from 0.28% to 2.07% predominantly as inorganic carbon (91%). For MSFA analysis, samples were split via metallic screen into +140 mesh and -140 mesh fractions to split the coarse gold from the fine gold.

Table 1. Powerline Deposit Sample Assays and 75 um Bottle Roll Results

The three representative master composites returned an average of 90.6% gold recovery using 75 um bottle roll testing. Overall gold extraction percentages ranged from 56.7% to 96.4%. These 75 um bottle roll tests show that gold recovery does not significantly change across variations in grade, depth from surface, sulphide content and lithology and that no organic carbon or other materials present preclude or reduce leach extraction rates (commonly referred to as non preg-robbing). The 75 um bottle roll tests had an average of 65% gold recovery within the first two hours and over 80% average gold recovery in the first 8 hours showing rapid gold recovery kinetics. Average cyanide consumption for the 75 um bottle rolls was low at 0.52 kg/t.

Industry standard comminution testing was completed on the composite samples to determine crusher work index (CWi), Bond's ball mill work index (BWi) and abrasion work index (Ai) parameters. The average CWi for the composites was 15.2 kWh/t and the BWi was 14.6 kWh/t, indicating Powerline is classified as medium to hard.

Gravity Recovery

Coarse gold is evident across Powerline and, therefore, gravity recovery was assessed as part of the Phase 1 program. Initial gravity recovery testing was completed on the three master composite samples and subsequently assayed as either rougher concentrate or cleaner concentrate. The Knelson concentrate produced the rougher concentrate, which was then further cleaned using a Gemeni table to produce the cleaner concentrate. Two grind sizes, 150 um (100 mesh) and 212 um (65 mesh), were tested throughout the gravity campaign, and the average gold recovery from rougher gravity concentrate was 53%.

Flotation

Flotation testing was conducted on all three composites across three different grind sizes: 150 um (100 mesh), 75 um (200 mesh), and 44 um (325 mesh). The tailings from the gravity recovery tests completed on the three composites were also assessed for flotation response at the 100 mesh particle size. All composites demonstrated high gold recovery in rougher concentrate with an average gold recovery of 89% from the composite samples (Table 2). Of significance is the overall low mass pull of ~3.7% on average. The high rougher flotation concentrate recovery along with the low mass pull suggests a small intensive cyanidation circuit leaching a flotation rougher concentrate as a process flow sheet option to be further investigated.

Table 2. Flotation Results for Powerline Deposit Composites