Archaean orogenic greenstone gold hosted in a number of different styles of mineralisation. Lode, supergene and palaeoplacer-style deposits characterise the range of ore body types.

St Ives lies within the Kambalda domain, a subset of the NorsemanWiluna Belt. The Kambalda domain is bound by the north-north west trending Boulder-Lefroy fault (BLF) and Zuleika shear. The region has undergone four compressional events predated by early extension and has been metamorphosed to upper greenschist or lower amphibolite facies.

The main structural feature of the St Ives area is the gently south-plunging Kambalda anticline, which extends 35 kilometres from the south end of the Kambalda dome to the Junction Mine. The majority of known gold deposits are proximal to the trace of the anticlinal axis. A major second order structure known as the Playa shear splays off the BLF shear zone and can be traced through the St Ives field for a distance in excess of 10km.

There are several styles of gold mineralisation at St Ives. The individual deposits may contain more than one of these styles:
- Lode mineralisation: Archaean lode mineralisation typically consisting of 0.5 to 20 metre-wide mesothermal vein complexes that may also have hydraulic breccia’s and/or mylonites, indicating movement on a shear
- Supergene mineralisation: Broad zones of flat-lying gold mineralisation in weathered
Archaean and overlying tertiary sediments
- Palaeoplacer mineralisation: Placer deposits hosted by palaeochannels in the unconsolidated tertiary sediments that overlie the Archaean basement.

St Ives currently operates one underground mine, which is accessed via a decline, and three open pits.

Conventional drill and blast with truck and shovel mining techniques are employed at all open pits. Grade control is generally by way of inclined RC drilling on grids determined by the ore body characteristics. Load-and-haul is carried out by 90 to 180 tonne dump trucks and 150 to 350 tonne excavators in backhoe and/or face shovel configuration. Mining benches vary from 5m to 10m, and are excavated in passes (flitches) of 2.5m to 3m per flitch. Gold mineralisation is mined selectively to cut-off grades, and segregated into grade ranges to balance the ore production and processing capacities onsite and to maximise cash-flow.

Underground mines at St Ives are commonly extensions of open pit mines. Mines are accessed via declines, drives are developed to access the ore and future stoping production areas. Underground mining at St Ives is predominantly mechanised and conducted by long hole open stoping (LHoS), with subordinate cut and-fill and room-and-pillar stoping for the shallower dipping ore bodies. Paste fill and LHoS is used where mandated by geotechnical factors. Electric-hydraulic drilling jumbos and rubber-tyred diesel-powered load, haul, dump machine (LHDs) are used for development and stoping, while trucks are used for load-andhaul operations. Ore from both open pit and underground operations is transported with road trains from individual mining operations to the central St Ives RoM pad.

The Lefroy Mill was commissioned in December 2004 and achieved design capacity within seven months. It treats medium- to high-grade ore through a 4.8 Mtpa variablespeed dual-direction 13.5 MW sag mill with wrap-around motor. Oversize from the mill (scats) is in closed circuit with a 140-tonne-per-hour pebble crusher. A gravity circuit recovers the gravity-recoverable gold from the milling circuit and the concentrate is treated separately through to bullion form. The mill cyclone overflow product flows to a five-stage leach circuit consisting of mechanical agitators, reagent addition and oxygen sparging.

Leached slurry passes through the six-stage carousel pump cell adsorption plant and subsequent five-tonne-capacity acid wash, elution and electrowinning circuits which produce calcine ready for smelting. Bullion is shipped to the refinery. Tailings are alternately deposited on two paddock-type tailings facilities which are constructed upstream.

Process optimisatio ........