Kanowna Belle is located in the Kalgoorlie Terrane (Boorara sub-domain) of the Eastern Goldfields Province.

Stratigraphically, the deposit sits in the Black Flag Group which overlies the lower volcanic sequences.

The Kanowna Belle deposit is hosted within a series of volcaniclastic sediments ranging in grain size from shale to conglomerates. These rocks are respectively separated into hangingwall and footwall sequences by a major 60° S-SE dipping zone of structural disruption and mineralisation.

The footwall sequence is dominated by the Golden Valley conglomerate, a mafic-dominated unit interbedded with the felsic-dominated Cemetery conglomerate. The hangingwall sequence comprises three mainvolcaniclastic units, these are the QED rudite, the Lowes sandstone and the Grave Dam grit, which is the dominant unit.
The sequence has been intruded by the Kanowna Belle porphyry, which is granodioritic in composition. At least 70% of the known gold mineralization is hosted by the Kanowna Belle porphyry, with the remaining mineralisation hosted by sedimentary units.

Gold in this mineralisation phase occurs mostly as fine grained (less than 10 microns (µm)) inclusions in pyrite or as very fine grained gold located in arsenic rich growth zones in pyrite. Free gold occurs in minor proportions, and typically occupies D2 extensional sites adjacent to pyrite crystals.

The Kanowna Belle gold deposit is mined by longhole stoping and underhand longhole bench stoping with paste fill methods. This mining method was selected to minimise the impact of mining induced stress on the underground operations through the use of geotechnical driven mining sequences and a fill system integral in the mining cycle.

The mining method used at Kanowna Belle underground is called longhole open stoping (LHOS). Mining of the LHOS commences with the development of drives (tunnels) on each level and the sides of these are supported by cement grouted roof bolts, mesh and shotcrete. These drives delineate the boundary of the stope. Each LHOS is 15-30m wide, up to 50m long and 120m high. Depending on size each stope may contain between 20,000 to 50,000 tonnes of ore.

The Kanowna Belle processing plant is a complex and versatile plant that includes separate circuits for processing free-milling and refractory gold ores. The plant has undergone incremental capacity increases since its initial construction and now has an annual throughput capacity of 1.88Mtpa. Processing at the current rate of ~1.82Mtpa of underground ore affords the processing plant the ability to substantially increase production should the need arise.

The crushing and grinding circuits are common for the free milling and refractory circuits.

The crushing circuit is a simple single stage circuit with a 240t capacity ROM bin feeding a Jaques double toggle 60x48 (185kw) crusher at a 420tph crushing capacity. The crushed ore, nominally minus 125mm reports to a 20,000t partially-covered coarse ore stockpile with a live capacity of about 1,000t.

This product is then reclaimed by an apron feeder and two vibrating feeders located under the stockpile and discharged onto a conveyor belt. The crushed ore is then conveyed to the grinding circuit.

The grinding circuit comprises an ANI Products 7.32m x 3.35m SAG mill operating in closed circuit with a Metso Nordberg HP200 recycle cone crusher and an ANI Products 4.72m x 7.01m Ball mill in closed circuit with cyclones. The SAG mill has a grate discharge and is steel lined, while the Ball mill has a trommel screen discharge and is rubber lined. The SAG mill has a variable speed drive with a range of 10 to 12 rpm, while the Ball mill has a fixed speed drive at 14.3 rev/min (75% of critical). The installed power for the SAG and Ball mills is 2,850kW. The grinding circuit throughput is currently around 160 – 190tph however it can be increased to 230tph if needed.

Pre-leach classification is achieved using a hydro-cyclone classifier circuit consisting of a cluster of 18 x 250mm cyclones that are fed from a central distributor. Only eight to nine of the cyclones are operated at any one time depending on volume of slurry in the milling circuit. Three of the cyclones in the cluster are dedicated to feed the Knelson gravity concentrator during the free milling ore campaigns. The cyclones are operated at a feed pressure of 110-130kpa.

The thickened slurry is pumped to the leaching and adsorption circuit where the recoverable gold is extracted by cyanidation. The cyanidation circuit is a traditional CIP circuit that consists of three leach tanks and six subsequent adsorption tanks. Oxygen is injected into the first two leach tanks by injection down the agitator shaft and also by injection into a Multimix Injector system installed within a pumped, recirculating slurry stream.

The slurry residence time in the CIP circuit is ~32 hours. Tank sizes vary across the circuit as a consequence of the 2007 circuit expansion project. The first two leach tanks (installed as part of the 2007 Expansion) have a working volume of ~1,400m3 each. The subsequent three tanks have working volumes of ~750m3 each and the final four tanks have working volumes of ~520m3 each.

The gold bearing steel wool is removed from the electrowinning cells, oxidized in a calcining oven and smelted directly with fluxes in a gas fired furnace. The smelt produces a vitreous slag containing all the base metals and impurities along with gold doré bars that contain ~70-85% gold and 15-30% silver.

The electrowinning, calcination and smelting processes are all performed inside a high security gold room.

For the free milling ores, the cyclone underflow stream from the three dedicated gravity circuit cyclones reports to a 1.8m wide by 4.2m long horizontal vibrating screen with 2.4mm by 15mm apertures to reject oversize material prior to feeding the Knelson Concentrator.

Gravity concentrate from the Knelson Concentrator is transferred in batches to a ConSep ACACIA Model CS2000 intensive leaching reactor to dissolve most of the gravity recovered gold. A concentrated caustic and cyanide solution (30% w/w NaCN) is heated to around 35°C and circulated through the concentrate bed for ~12 hours. The gold bearing solution is transferred to a storage tank for circulation through electrowinning cells for ~12 hours.

The roasting process makes the concentrate particles porous by burning off the sulphur and arsenic that surrounds the very fine gold particles. The porosity permits cyanide leaching and recovery of the otherwise occluded gold particles.

Ore from the Kundana operations is treated at the NST owned Kanowna Belle processing facility located adjacent to the Kanowna Belle mine.