The majority of the Peak deposit lies between 300 m and 700 m from surface and extends over a strike length of 300 m along the Peak Shear. A low grade oxide resource exists from surface to the base of oxidation, some 70 m below surface. In a broad sense, the deposit is vertically elongate parallel to the dominant steep west dipping cleavage and the strike of the Peak Shear Zone. The mineralized system is thickest around the volcanics, where it attains a maximum thickness of 150 m, and rapidly tapers upwards into the overlying sediments
along the shear zones.

The majority of higher grade mineralization is controlled and localized about the apical portions of a series of flow banded rhyolite and rhyolitic subvolcanic breccia bodies. These rhyolites and rhyolitic breccias do not outcrop and are only known from drill core and underground openings. These bodies are shallowest in the centre of the Peak deposit where they are located 450 m from surface. They are known to extend at least 1,000 m south, 500 m north, and 300 m east of the deposit.

The Peak deposit consists of discrete lenses of mineralization. The lenses generally strike and dip parallel to the pervasive regional cleavage, that is, they trend north-south and are subvertical to steep west dipping. Another series of northwest trending, moderately southwest dipping lenses are localized about the southern contact of the eastern rhyolitic body.

The lenses consist of a series of narrow, stacked en-echelon veins and are elliptical to thin lensoidal shapes in plan. The host structures have strong vertical continuity, persisting at depth below the currently defined deposit. Economic mineralization is less continuous within the host structures. Within each lens, gold grades are highly variable in all directions.

Four styles of gold and associated base metal mineralization occur at Peak:

1. Sediment Hosted – Sheeted veins to 200 mm wide of quartz+sphalerite+galena+chalcopyrite+gold occur in zones of intensely silicified sandstones and lesser siltstones of the Chesney Formation. The vein sets are parallel to the welldeveloped,
steep west dipping cleavage. The Western Lead Zinc (WLZ) lens is the largest example of this style of mineralization at Peak.

2. Contact Zone Hosted – The Contact Zone is defined as the zone of altered sediment at the sheared contact with rhyolite and volcanic breccia. These zones are of arcuate geometry and surround the western margin (and lesser eastern margin) of the subvolcanic bodies. The contact zones contain lenses of disseminated to semimassive pyrrhotite+chalcopyrite+sphalerite+
galena+gold mineralization with quartz gangue.

3. Volcanic Hosted – En-echelon quartz veins within riedel shears in the eastern volcanic breccia bodies host pyrrhotite+chalcopyrite+
galena+sphalerite+Au mineralization. These lenses lie within the dominant cleavage and vary in thickness from one metre to twenty metres. The Terror Lens is the largest lens of this style.

4. Late Stage Shear Hosted–Small discontinuous pods of banded to semi-massive sphalerite-galena-chalcopyrite-pyrrhotite-pyrite carrying high grade silver and patchy gold mineralisation associated with black chlorite-talc-carbonate alteration are
developed in late shears including the Peak/Polaris Shear and the Hecla Shear.

Current mining operations are located in two mining zones. The Peak mining zone includes Peak, Perseverance, and New Occidental orebodies. The New Cobar mining zone to the north includes Chesney and New Cobar orebodies.

At Peak, Perseverance, New Occidental and New Cobar, the mining is done by bench stoping. At Chesney, a combination of bench stoping and open stoping is planned. Mining progresses from bottom up in each panel.

New Cobar was mined by open-pit methods until early 2004. The currently active New Cobar mining zone is below the open pit and is accessed via a ramp from within the open pit. The Chesney orebody is accessed from a 700 m decline from the New Cobar ramp system. The underground workings for access to the New Cobar and Chesney zones are separate from those workings that access the Peak, New Occidental, and Perseverance zones.

Underground development is carried out using standard electric-hydraulic twin-boom jumbo drills with emulsion for blasting. Development headings are supported with a combination of split-sets, resin bolts, mesh, and fibre reinforced shotcrete.

Blasted headings are loaded with Load-Haul-Dump (LHD) units. Development ore is loaded into 55 t trucks and hauled to the underground crusher at Peak or to the surface stockpile at New Cobar.

Sublevel open stoping is used where conditions allow. Panels approximately 100 m high (four sublevels) are mined from the bottom up. In areas where walls are less stable, modified retreat benching is employed. In these areas, 20 m to 35 m sublevel intervals are mined and loose waste is backfilled into the stope void as mining retreats along strike.

Processing ore through the PGM processing plant involves grinding, cyclone classification, gravity separation, flotation, concentrate filtration, Carbon in Pulp (CIL) leaching, elution, carbon regeneration, electrowinning, and smelting. Feed to the plant is crushed underground; suitable for semi-autogenous grinding (SAG) mill feed.

Ore from the Perseverance and New Occidental deposits is crushed underground and hoisted to the surface via the Peak mine shaft. It is discharged onto a surface stockpile from where it is reclaimed via feeders under the stockpile and fed to the SAG mill. Ore from the New Cobar and Chesney mines is trucked to a Run-of-Mine (ROM) pad stockpile. It is reclaimed by a front end loader and fed via a hopper onto the SAG mill feed conveyor.

Feed rate to the SAG mill is around 104 tph. SAG mill discharge feeds onto a double deck vibrating screen with a 16 mm top deck screen aperture size and 2 mm bottom deck aperture size. Plus 16 mm material reports to a scats (critical size material) pile where it is returned to the grinding circuit feed using a loader. Minus 2 mm material is pumped to three Knelson concentrators where a gold concentrate containing free coarse gold is recovered and sent to a Gekko intensive leach reactor (ILR). The gold rich eluate is then pumped to a dedicated electrowinning cell in the gold room.

The Knelson tail is combined with the -16 mm +2 mm material from the vibrating screen and pumped to a bank of hydrocyclones. Cyclone underflow reports to a ball mill for further grinding. Ball mill discharge combines with SAG mill discharge. Cyclone overflow with an approximate P80 75 µm reports to the flotation circuit. The flotation circuit consists of one column rougher and an Outotec Convention Flotation Cell system. The Outotec system was commissioned in March 2011 and contains three rougher OK28 cells, three scavenger OK28 cells, and five cleaner OK3 cells. Flotation concentrate is thickened, filtered and discharged onto a concentrate storage pad. From there it is blended and loaded in to shipping containers and trucked off site.

Flotation tails report to a thickener and are then fed to the CIP circuit. In the leach circuit, gold is dissolved and adsorbed onto activated carbon. The gold loaded carbon is sent to the elution circuit where it is recovered into a gold rich eluate and pumped to the gold room for electrowinning in a dedicated electrowinning cell. The stripped carbon is regenerated and returned to the leach circuit. The leach circuit tails are thickened to 60% density and pumped to the central discharge tailings storage facility.

Pregnant solutions from the CIL elution and gravity circuits are electrowon in separate electrowinning cells. The gold is recovered onto steel wool cathodes. The cathodes are cleaned weekly to remove the gold bearing sludge. The sludge is then filtered and dried. For accounting purposes, the dry sludges from the gravity and CIL circuits are smelted individually.