CGO is located in the Achaean Murchison Province, a granite-greenstone terrane in the northwest of the Yilgarn Craton. Greenstone belts trending north-northeast are separated by granite-gneiss domes, with smaller granite plutons also present within or on the margins of the belts.

Mineralisation at Big Bell is hosted in the shear zone (Mine Sequence) and is associated with the post-peak metamorphic retrograde assemblages. Stibnite, native antimony and trace arsenopyrite are disseminated through the K-feldspar-rich lode schist. These are intergrown with pyrite and pyrrhotite and chalcopyrite. Mineralisation outside the typical Big Bell host rocks (KPSH), for example 1,600N and Shocker, also display a very strong W-As-Sb geochemical halo.

Numerous gold deposits occur within the Cuddingwarra Project area, the majority of which are hosted within the central mafic-ultramafic ± felsic porphyry sequence. Within this broad framework, mineralisation is shown to be spatially controlled by competency contrasts across, and flexures along, layer-parallel D2 shear zones, and is maximised when transected by corridors of northeast striking D3 faults and fractures.

The Great Fingall Dolerite hosts the majority gold mineralisation within the portion of the greenstone belt proximal to Cue (The Day Dawn Project Area). Unit AGF3 is the most brittle of all the five units and this characteristic is responsible for its role as the most favourable lithological host to gold mineralisation in the Greenstone Belt.

The Big Bell Trend is mineralised a strike length of >3,900m, a lateral extent of up +50m and a depth of over 1,500m.

Great Fingall is mineralised a strike length of >500m, a lateral extent of >600m and a depth of over 800m.

Black Swan South is mineralised a strike length of >1,700m, a lateral extent of up +75m and a depth of over 300m.

The Tuckabianna plant receives underground ore from the large Big Bell underground and the smaller Comet underground mines as well ore from the Cuddingwarra open pits.

While Big Bell is the primary producer of ore to the Tuckabianna mill, the Comet underground mine has served well as a supplementary source and is expected to continue as such in FY22. After three years of dewatering, mine rehabilitation and refurbishment, Big Bell mine production began to rise in FY21 with steady state operations expected to be achieved in FY22.

A number of open pits commenced at CGO in FY2021 including a new mining hub at Cuddingwarra North and open pits at Jim’s Find and City of Chester.

Exploration and viability studies were carried out during FY2021 at the previously mined Fender open pit mine on the southern limits of the Big Bell shear, testing the economics of a transition to underground operations with this potential development scheduled to commence during FY22.

Open Pit
A majority of the open pits have a final design wall angle of 39-46 degrees. Dilution of the ore through the mining process has been accounted for within the Ore Reserve quoted inventory. Various dilution ratios are used to represent the style of mineralisation. Minimum mining widths have been accounted for in the designs, with the utilisation of 40t or 90t trucking parameters depending upon the size of the pit excavation.

Underground
In large disseminated orebodies sub level caving, sub level open stoping or single level bench stoping production methodologies are used. In narrow vein laminated quartz hosted domains a conservative narrow bench style mining method is used. In narrow flat dipping deposits a Flat Long Hole process is adopted (with fillets in the footwall for rill angle) and or jumbo stoping. Minimum mining widths have been applied in the various mining methods.

CGO (Cue Gold Operations) incorporates the 1.2-1.4 Mtpa Tuckabianna processing hub. The Tuckabianna processing hub treated 1,261,129 tonnes of ore, within the mid-range of the plants operating capacity and in line with expectations. The metallurgical recoveries rate for the ore blend was 88.21%.

CGO has an existing conventional CIL processing plant.

Gold extraction is achieved using two staged crushing, ball milling with gravity concentration and Carbon in Leach.

A high portion of the Reserve mill feed have extensive data when processed at other plants in the past 2-3 decades. This long history of processing demonstrates the appropriateness of the process to the styles of mineralisation considered.

No deleterious elements are considered, as a long history of processing has shown this to be not a material concern.