The flotation recovery remained at 97% and the leach recovery increased to 93.6%, giving an overall recovery of 90.1% 3. Since 2017 head grades have exceeded 20g/t Au. The similarities between Fosterville and Reefton support the testwork results on Reefton samples 1 to 7 and the proposed flowsheet. A review of Sam's Creek testwork conducted by GRDMacraes in 2004 identified the potential for 84% gold recovery via whole of ore direct leach and 91% gold recovery with flotation, concentrate oxidation and cyanide leach.

The testwork identified a promising response to flotation with 9698% of the gold reporting to the concentrate at a mass pull of ~6%. Mineralogical, petrographic and geochemical analysis supported the testwork findings that the gold is finely disseminated within a sulphide matrix, predominantly arsenopyrite, galena and chalcopyrite 4. A flowsheet similar to that proposed for Siren's Reefton resources would therefore be applicable. In 2004 Laboratory test work was reported by GRD-Macraes on four composite samples from Sams Creek diamond core.

Direct leaching, flotation and leaching of the flotation concentrate were tested. The four samples were each ground to an unspecified sizing but the report states the grind time was twice as long as the Macraes ore. A flotation concentrate over 26 minutes was produced with high gold and sulphur recoveries.

Gold recoveries ranged from 95.6% to 97.7% and sulphur recoveries from 92.6% to 94.4%. Flotation tailings were low enough in gold for disposal. Three sets of cyanide leach tests were reported.

The first tests were leaches on the samples after grinding. As shown below gold extractions ranged from 79.3% to 87.5%. The results demonstrate that there is a component of refractory gold present.

The second and third cyanide leach tests were on the flotation concentrate. One test leached the flotation concentrate as received and the other test conducted a nitric acid leach (effectively an oxidation step) followed by a cyanide leach. The leaches on the flotation concentrate as received again confirm the presence of a refractory component which also floated, hence is presumably a sulphide.

Three of the four acid (oxidation) leaches improved recoveries by 5% to 15% except for sample 4. There is no information in the test results to explain this result. Of note no gravity testwork was conducted. In summary the Sams Creek samples exhibited a small degree of refractory gold.

High gold recoveries were achieved by flotation and, after an oxidation step, gold extractions ranged from 88.6% to 95.5%. Stibnite (antimony sulphide) has been seen in significant quantities in the Reefton goldfield. Stibnite is generally associated with gold mineralisation and in various Au-Sb operations around the world, free gold is recovered by gravity, followed by the production of a stibnite flotation concentrate.

The Brunswick Processing Plant at the Mandalay Resources Costerfield Mine in Victoria has a flowsheet which is simple, conventional and a well-proven circuit, with more than 14 years of operation. The surface crushing and screening facility processes underground ore feed down to a particle size range sui for milling through a two-stage, closed circuit ball milling circuit. Centrifugal style gravity concentrators are used on the combined primary milling product and secondary mill discharge to recover a gold-rich gravity concentrate.

This is upgraded further over a shaking and sold as a separate gold concentrate product, which is transported to local refineries. Secondary milled products are classified according to size and processed through a simple flotation circuit comprising of rougher, scavenger and single stage cleaning. The flotation concentrate is dewatered through thickeners and with filtration to produce a final antimony-gold concentrate product, which is bagged, packed into shipping containers and shipped to customers overseas.

The feed to the plant during 2020 and 2021 was between 11.0 and 12.1g/t Au and 3.5 to 4.5% Sb. The gravity gold production varies but recoveries are typically around 40 to 50%. The 2021 end of year (EOY) reconciled plant recoveries were 94.6% Sb and 93% Au, with the gold not recovered by gravity reporting to the flotation concentrate 45.

Should Au-Sb resources be delineated at Reefton the metallurgical solution is anticipated to be a simple and straightforward process. Based on the testwork reported above, GRES reviewed the process design criteria and flowsheet that was presented in the phase 1 Scoping Study. Little change was required, and the key features of the process plant are as follows: A nominal processing capacity of 1.25 million tonnes per annum, using a design head grade of up to 10g/t Au to cater for surges of high-grade ore.

Three stage crushing, With fine ore bin storage and emergency reclaim. Single stage ball mill, with a flash flotation cell treating cyclone underflow. Separate gravity concentrators to treat ball mill discharge and flash flotation concentrate to produce Doré bullion output of up to 80% of the gold in the feed, again to handle high grade surges.

Gravity plus flotation of approximately 93%, with an overall recovery estimated at approximately 90% with POX. Concentrate dewatering utilising a thickener and a filter to produce a transpor concentrate. Appropriate tailings handling facilities depending on plant location and underground paste fill requirements.

Steinert Ore Sorters to reduce waste from the mining cycle and increase mill feed head grade. Steinert Ore Sorters reduce waste from the mining cycle, minimise transport costs and increase mill feed head grade. Samples from Alexander River and Sams Creek ore and waste are being tested by Steinert.

Sensor Sorter Results from the theoretical sort have indicated potential for separation using STEINERT's combination Sensor Sorter.