The KOTH mineralisation is considered to be part of an Archean Orogenic gold deposit with many similar characteristics to other gold deposits within the Eastern Goldfields of the Yilgarn Craton.

Gold mineralisation is associated with sheeted and stockwork quartz vein sets within a hosting granodiorite stock and pervasively carbonate altered ultramafic rocks. Mineralisation is thought to have occurred within a brittle/ductile shear zone with the main thrust shear zone forming the primary conduit for the mineralising fluids. Preexisting quartz veining and brittle fracturing of the granite created a network of second order conduits for mineralising fluids.

Brittle fracturing along the granodiorite contact generated radial tension veins, perpendicular to the orientation of the granodiorite, and zones of quartz stockwork. These stockwork zones are seen in both the granodiorite and ultramafic units and contain mineralisation outside the modelled continuous vein system (High Grade Veins).

Gold appears as free particles (coarse gold) or associated with traces of base metals sulphides (galena, chalcopyrite, pyrite) intergrown within quartz along late stage fractures.

The Western Flank mineralised zone strikes 30 degrees west of true north over a distance of 700m and plunges to the southwest. Individual lodes dip east at 35 to 45 degrees. Eastern Flank mineralisation strikes 30 degrees east of true north over a distance of 700m and is vertical. Stockwork mineralisation runs along the contact of the granodiorite/ultramafic contact which strikes 30 degrees east of true north over a distance of 4km and is vertical. Mineralisation has been tested to approximately 400m below surface and remains open.

The mining methods for underground is a mix of narrow to large scale open stoping and air leg room and pillar. Minimum height is approximately 3.8m with Jumbo development and 3.0m for air leg development with the resource reported on similar size panels to reflect this relationship.

KOTH is currently an operating underground gold mine, and the KOTH FFS is predicated on the continuation of existing underground mining practices. Mine design parameters are based on current site guidelines, which are well understood and have been successfully implemented.

The proposed primary mining method is long-hole open stoping, with minor amounts of airleg stoping in flat dipping areas of the orebody (<1% of ore tonnes). Stoping will follow a top-down sequence, commencing at the extremities of each level and retreating to the level access. Rib pillars will remain between adjacent stopes to maintain mine stability. The proposed mining methods and sequence are generally a continuation of current operating practices at an increased production rate.

Areas identified for long-hole stoping are categorised as narrow vein or bulk stoping. The narrow vein parameters include a 2.0 m minimum stoping width in combination with a 20 m level spacing, whereas the bulk stoping parameters include a 3.0 m minimum stoping width in combination with a 40 m level spacing.

Cut-off grades were estimated for the different mining methods, and stope shapes were generated using MSO software based on a provisional cut-off grade of 1.8 g/t.

A mine development design was created to match the stope optimisations. Modifying factors based on geotechnical evaluation and historical performance were applied to the mine plan and schedule. Mining dilution of 10% and mining recovery ranging between 85% - 95% was applied dependent upon the mining method.

Mine infrastructure requirements have been included in the mine plan, including power, water, emergency preparedness, and ventilation. The latter has been evaluated in simulation software and accounts for life of mine ventilation requirements.

The underground mine is planned to be accessed via the existing portal located in the KOTH open pit.

The assumed operating regime at KOTH involves the use of a mining contractor, consistent with current practices. The incumbent mining contractor (Pit N Portal-Emeco) has reviewed the mine plan and schedule and provided a detailed cost estimate for the FFS underground mining costs.

Underground mining may continue beyond FY27 as a result of further in-fill and exploration drilling. Extensional drilling will benefit from the installation of drill platforms as development progresses. The extension of the underground mine life would allow the mine to continue to produce at peak gold production rates and a lower AISC beyond FY27.

Mine operations at KOTH were suspended on 15 January 2021. The KOTH underground mine is currently being maintained in a standby state with pumping, ventilation and electrical reticulation remaining active.

The King of the Hills Underground mine is an operating asset in full production.

Underground mine development activities continued during the 2022, with over 800 metres of development completed. The first stope was fired in June 2022, signalling the commencement of underground production activities. Underground infrastructure is still under development, with connection to the site high voltage system to occur early in the September Quarter.

Mining infrastructure establishment continues, with the completion of the heavy vehicle workshop, offices, change rooms, ablutions and training facilities expected in the September 2022 Quarter.

Open Pit
In 2022 Macmahon mined 2.9 million bank cubic metres (Mbcms) in the June Quarter from the Stage 1 pit, including 365,675 tonnes of ore at an average grade of 0.52g/t (consistent with the expected grade of ore mined at this stage of the open pit cut-back). Land clearing for the waste storage facility is progressing to plan, drill and blast activities are on plan.

The mining method proposed for all deposits is the conventional use of excavators in backhoe configuration as the primary loading fleet, loading rigid off-highway rear dump trucks. This configuration is common to the Goldfields region of Western Australia (WA) and is considered a low-risk solution.

There is 1.5Mdmt of TMM in the March Quarter 2022, comprising 870 k dmt of waste and 630 k dmt of ore. The waste material is being classed as capitalised pre-strip to access a sustainable source of ore feed at KOTH for subsequent periods. The ore is placed on the ROM pad.

Mining at Rainbow starts in June Quarter 2022 and is completed 15 months later. While waste movement is required to access ore, sustainable ore production occurs within the first quarter of mining, and therefore the waste has not been defined as capitalised pre-strip. It should be noted, however, that the ore will likely only become available in the latter half of that quarter.

There is a contingency for ensuring continuity of ore feed in the initial year of process plant operation with approximately 1.7Mdmt of ore on existing surface stockpiles.

Mining at Cerebus-Eclipse starts in 2029 and continues for 12 months, with Centauri being a continuation of operation for the mining fleet, starting in 2030. The haul road and infrastructure used at Cerebus-Eclipse will be used for the Centauri operation.

The general progression of the production schedule for KOTH is from south to north, depleting the southern half of the pit in time for the short haul of waste from the northern cut-backs. Depleting the southern half of the KOTH pit also results in the open cut mining operation avoiding the UG portal and vent raise for the UG operation mine plan. This approach removes the requirement for any capital works required in establishing a new portal, providing access to that portal location (both surface and underground) and establishing supporting underground infrastructure such as a new vent raise.

While the average grade of the southern half of the pit is not as high as in the northern half of the pit, the lower strip ratio in the south compensates for this lower grade and provides earlier access to sustainable ore supply.

Waste from the open pits will be dumped on a ‘short haul first’ logic. From an immediate cost perspective, this is advantageous; however, this approach will need to be balanced with the levelling of truck numbers over the LOM, so as not to incur additional mobilisation/demobilisation costs for short periods of operation.

The waste dump capacities as designed can contain all waste from the pits. The KOTH external waste dumps do exceed the recommended height limits later in the LOM, which will need to be proactively addressed during the operational period.

The primary mining fleet for the KOTH open pit are 250 t class excavators (in backhoe configuration), paired with 140 t class haul trucks.

The primary mining fleet for the satellite deposits is one 120 t class excavator (in backhoe configuration), paired with five 100 t class haul trucks.

KOTH is currently an operating underground gold mine, and the KOTH FFS is predicated on the continuation of existing underground mining practices. Mine design parameters are based on current site guidelines, which are well understood and have been successfully implemented.

The proposed primary mining method is long-hole open stoping, with minor amounts of airleg stoping in flat dipping areas of the orebody (<1% of ore tonnes). Stoping will follow a top-down sequence, commencing at the extremities of each level and retreating to the level access. Rib pillars will remain between adjacent stopes to maintain mine stability. The proposed mining methods and sequence are generally a continuation of current operating practices at an increased production rate.

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Successful commissioning of the new 4.7Mtpa processing plant, crushing circuit and power station completed, with first gold poured on 5 June 2022 and now ramping up towards steady-state operations.

The first gold pour from the process plant was achieved on 5 June 2022. During June 2022, the total mill operating time was 84%. The SAG mill continues to deliver throughput rates in excess of 600 tonnes per hour for significant periods at moderate mill loads and power draw.

The KOTH processing facility has essentially been designed to process 4Mtpa of fresh open pit and underground ore. However, allowance has been incorporated into the design for future throughput upgrade to 6Mtpa with limited production interruption and low capital requirements. The primary crushing circuit has been designed for 6Mtpa. The mill selection and the layout of the grinding circuit allow for a future ball mill, with allowance provided for a second gravity recovery line. The design also allo ........