The operation consists of two open pits in the Saddleback Greenstone Belt, a fault bounded sliver of Archaen volcanic and shallow level intrusive rocks surrounded by granite and gneissic rocks. The main zone of gold mineralisation occurs over a strike length of more than five kilometres and a width of approximately one kilometre.

Boddington is mined by a conventional truck-and-shovel operation. Equipment is owneroperated and includes a large mining truck fleet (240-tonne class), electric rope shovels, support equipment, and drills. Mining is done predominantly on 12 m benches.

The mine operates two pits (North & South Pits) utilizing three CAT electric shovels and 39 CAT 793 haul trucks. Boddington has a current capacity to mine approximately 235,000 tonnes of material per day.

The milling plant includes a three stage crushing facility (two Primary crushers, six Secondary crushers and four high pressure grinding rolls), four ball mills, a flotation circuit and carbon in-leach circuit. The flotation circuit process recovers gold-copper concentrate before the material is then processed by a traditional carbon-in-leach circuit where the remaining gold is recovered to produce doré.

The processing plant has a nominal capacity to process approximately 40 million tonnes of ore per year with optimization projects underway to further increase this capacity.

The process consists of primary crushing, closed circuit secondary and High Pressure Grinding Rolls (HPGR) tertiary crushing, ball milling, and hydrocyclone classification to generate a milled product with a P80 of 150 micrometers (µm) at a slurry density of around 35% solids.

The cyclone overflow from the mill circuit is treated in a flotation circuit that produces a copper–gold concentrate for export. Rougher and scavenger flotation concentrates are reground and cleaned to achieve an acceptable final concentrate grade. The concentrate is thickened and filtered before being trucked to port.

The cleaner scavenger tailings stream is thickened and leached under elevated cyanide levels. The scavenger tailings are thickened and leached in a conventional leach/adsorption circuit. The leached slurry from the cleaner scavenger tailings leach circuit is delivered to the scavenger tailings circuit for combined recovery of gold. Leach residue is pumped to the residue disposal area, and residual cyanide is maintained below a targeted level by a Caros acid cyanide destruction plant.

The carbon from the scavenger tailings adsorption circuit is treated by conventional splitAnglo American Research Laboratory method elution and reactivated in horizontal reactivation kilns. Gold recovery from the eluate is by electrowinning, cathode sludge filtration and drying, and smelting.

There is a flash flotation and gravity circuit installed in the process plant. These circuits have not been operated and remain decommissioned.

Coarse Crushing (in mining area)
The mine haul trucks dump ore to two primary crushers (60/113 MK-II gyratory crusher). Crushed ore is transferred via an overland conveyor to a 230,000 t capacity (40,000 t live capacity) stockpile adjacent to the processing plant. Dozers operating on the coarse ore stockpile can increase the total storage capacity up to 400,000 t.

Fine Crushing and Screening (process plant)
Three apron feeders reclaim ore from beneath the coarse ore stockpile and delivers the ore to the secondary crusher feed conveyor and the six secondary crushers (MP1000 cone crusher, five original with a sixth crusher installed in late 2010), which are operated in closed circuit with four coarse screens (three original with a fourth coarse screen installed in 2010).

Oversize material returns to secondary crushing and the fine material reports to the tertiary crushing plant that consists of four HPGRs. The tertiary product is stored in a 20,000 t fine ore bin ahead of the ball milling circuit. Fine ore is reclaimed from the bin via eight reclaim belt feeders (two per four parallel milling trains) and delivered to the fine screens ahead of ball milling. Each line consists of two screening units.

Undersize material from the screens reports to one of four cyclone feed hoppers and the oversize returns to the HPGRs for additional crushing. Cyclone clusters classify the finely-crushed particles, with the finer cyclone overflow material (80% passing 150 µm) reporting to the flotation distribution box and the coarse cyclone underflow material to a split between the ball mills or flash flotation cell (for free gold recovery).

Concentrate from the flash flotation cell feeds a gravity circuit where gold is concentrated prior to intensive cyanidation, electrowinning and smelting. The flash flotation circuit is currently not operating, due to water balance issues associated with the grinding circuit. Tails from the flash flotation cells are recycled back to the ball mills for further grinding. The target final product grind size from the milling circuit is 80% passing 150 µm, although increased throughput rates in 2011 and 2012 resulted in grind size P80 coarsening to 170 to 190 µm at times. Improved process control and increased ball mill operating power draws have reduced the grind size back to around 150 to 160 µm at the elevated throughput rates.

Gold and Copper Recovery to Concentrate The flotation distribution box transfers cyclone
The flotation distribution box transfers cyclone overflow product from each of the four parallel grinding lines in to three parallel trains comprising, eight-unit flotation cells. Concentrates produced by cells #1 and #2 report to the coarse cleaner cells for final cleaning, and product from the other cells reports to regrind thickening.

The regrind plant consists of two Verti-mills (one duty and one standby) with product reporting, via cyclone clusters, to the cleaner flotation plant. The cleaner flotation facility has three sequential stages with final product being transferred to the concentrate thickener, then storage in two, 1,000 m3 tanks before being sent to the filtration plant. Concentrate is trucked to the port of Bunbury to be exported by sea.

The cleaner circuit has a scavenger circuit consisting of six cells. Cleaner scavenger tailings are leached in a dedicated circuit of nine leach tanks with the product combining, for further leaching, with the tails from the eight-unit flotation cells.

Gold Smelting and Bullion Production
Scavenger flotation tails report via a flotation tailings thickener to two five-unit leach tank trains. From the leach tanks, it transfers to two trains of seven carbon-in-leach (CIL) tanks and finally transferring to the residue disposal area (RDA). Activated carbon used in the leaching process to adsorb gold leached into solution reports to a two-train elution plant. Each elution plant has two elution columns, two heat exchangers and two elution heaters. The barren carbon product from the elution columns is transferred to the carbon reactivation plant before transfer back to the CIL train, and the gold solution transfers to the electrowinning circuit. The final product from the eight-unit electrowinning circuit reports to the gold furnace for smelting.