Buckreef Mine PEA (Report No. 473)

This report describes the proposed expansion of the Buckreef processing facility from its current configuration to a 3,000 tpd circuit incorporating flotation and fine grinding for sulphide ore treatment.

Report context

This preliminary economic assessment (PEA) for the Buckreef Mine, Report No. 473, was prepared for TRX Gold Corporation. The processing section (Section 17.0) presents recovery methods for the Buckreef Deposit, drawing on expansion modelling by Orway Mineral Consultants (WA) Pty Ltd (“OMC”) summarised in “Buckreef Gold Project Expansion Review, Report No. 7833” dated January 6, 2025.

Processing route

Existing operations (historical operating data)

In April 2020, TRX initiated mining of Buckreef’s oxide mineralization and processing up to 60 tpd via an on-site pilot oxide gravity CIL plant. The plant was expanded in 2022 to 360 tpd, and again in 2023 with the addition of a 1,000 tpd capacity ball mill expected to process both oxide and sulphide mineralization. In July 2024, the Company announced plant expansion to 2,000 tpd, averaging 1,750 tpd of process plant throughput.

The current processing facility consists of two trains of three-stage crushing, four closed circuit ball mills, eleven carbon-in-leach (“CIL”) tanks, and complete elution (less reactivation kiln), electrowinning, and smelting for the production and sale of gold doré.

Proposed expansion design (Phase 1 and Phase 2)

Expansion modelling by OMC confirmed that to improve recovery, an expanded circuit needs to include flotation and fine grinding. A rationalisation of the flowsheet was undertaken to finalise the process plant consolidated flowsheet containing the following unit operations:

• Existing Primary Crushing;
• New Surge Bin with overflow to dead stockpile and reclaim;
• Retire Secondary and Tertiary Crushing, and product screening;
• New SAG Mill;
• Existing 1,000 tpd Ball Mill;
• New Classification;
• New Flotation;
• New Flotation Concentrate Regrind Circuit;
• New Flotation Concentrate Regrind Thickener;
• New Flotation Tails Leach Feed Thickener;
• New Flotation Concentrate Regrind Leach Circuit with potential to add oxygen addition;
• Existing Modified CIL 3 Flotation Tails Circuit;
• New Split AARL Acid Wash and Elution Circuit;
• New Carbon Regeneration Kiln; and
• Existing Tails Storage Facility.

Comminution would be via primary crush, surge bin, overflow to dead stockpile with front-end loader (“FEL”) reclaim, and grinding via SAG and ball mill circuit that would incorporate the existing ball mill No.5. Flotation of a sulphide concentrate and regrinding to P80 15 µm was included. Thickening of both the concentrate regrind stream and flotation tails stream was included to improve leaching performance and reduce cyanide consumption. Two new leach tanks of identical size to the CIL 3 tanks would be added for concentrate regrind leaching, which would then join the flotation tails feed to CIL 3 through the existing tankage. A new split AARL elution circuit with a dedicated acid wash column and subsequent carbon regeneration kiln was adopted to improve carbon activity and reduce soluble gold losses to tails.

Expansion circuit modelling was undertaken for two throughputs: Option (Phase) 1 – 2,000 tpd (current – 1,750 tpd); Option (Phase) 2 – 3,000 tpd (2,960 tpd nominal).

Phase 1 has a production target rate of 1,750 tpd (636,738 tpa) for YR1 and YR2 with capital expenditures for the following major equipment: Flotation Circuit (trash screens, reagent conditioning tank, and five Metso e50 tanks cells (50 m³/cell) and blower system); Flotation Concentrate Regrind Mill (High Intensity Grinding (“HIG”) Metso HIG700); Pumping and Cycloning within Regrind Circuit; Concentrate Leach Feed Thickener (16.5 m diameter); Two additional CIL Tanks to treat Flotation Concentrate; Flotation Tailings Thickener (16.5 m diameter); 4 tpd Elution Circuit; and Associated Screens, Pumps, Reagent System, and upgraded Water System.

During operations in Phase 1, expansion will be underway for an increased production target rate of 3,000 tpd (1,080,000 tpa) for YR3. With a planned grinding target of P80 at 100 – 150 µm, capital expenditures are planned for: SAG mill circuit Surge Bin, Feeders, Conveyors; SAG Mill (7.32 m diameter x 3.75 m Effective Grinding Length, 3,500 kW); Cyclone Cluster with SAG and Ball Mill(s) Circuit; Reverting to Single Toggle Jaw Crusher (750 m x 1,069 m for SAG mill feed prep); and Cyanide Destruction System (to coincide with underground mine construction).

Water management (historical and proposed)

Surface water is scarce in the Project area. The main surface water source is the Nyamazovu River, a small stream which has been used as a fresh water supply for the process plant. The current Buckreef operation has an efficient system in place to conserve and recycle water including process, mine and storm water. Current water requirements are 2,644 m³/day for processing approximately 1,488 tpd (Mills 2, 3, 4 at 440 m³/d each; Mill 5 at 1,320 m³/d; total 2,640 m³/d; Elution columns totalling 6.3 m³/d). Water requirements for the Phase 1 and Phase 2 expansion are approximately 5,200 m³/day.

Key reported parameters

Technical qualifications

The report recommends that cyanide destruction testing be conducted at an external laboratory. Further metallurgical testwork is recommended on comminution, confirmatory flotation, thickening, rheology of flotation tails and concentrate, and concentrate leach test at 40% solids, P80 of 100 – 150 µm with oxygen sparging and kinetic sampling to confirm that the predicted recovery of the proposed circuit is achievable.

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Source: TRX Gold Corporation, Buckreef Mine PEA, Report No. 473, Section 17.0 Recovery Methods (pages 243-255)