The Rosebery volcanogenic massive sulphide (VMS) deposit is hosted within the M t. Read Volcanics, a Cambrian assemblage of lavas, volcaniclastics and sediments deposited in the Dundas Trough between the Proterozoic Rocky Cape Group and the Tyennan Block.

Sulphide mineralisation occurs in stacked stratabound massive to semi-massive base metal sulphide lenses between the Rosebery Thrust Fault and the M t. Black Thrust Fault; the host lithology and the adjoining faults all dip approximately 45 degrees east.

Economic Zn-Pb-Ag-Au mineralisation occurs as massive, semi massive and disseminated base metal sulphide lenses located within the Rosebery host sequence.

Mining production carried out by long-hole open stoping. The majority is a longitudinal retreat while some limited areas are by wider transverse stopes. This method is appropriate for mining the style of mineralisation in the view of the competent person.

The lenses are divided into panels and are mined using a bottom-up sequence in a continuous 45 degree retreating front towards the level access drives. The nature of this mining sequence causes fluctuations in the grade profile of the short term schedules. Stoping panels contain between 3 and 5 sub-levels with crown pillars left in-situ between the backs of up-hole stopes and the lowest sill drive of the panel above.

Backfilling of stope voids is carried out using two methods; Cemented Rock Fill (CRF) and Rock Fill (RF).

Access to the orebody is through a decline 5.5m x 5.5m at a 1:7 gradient. The standoff distance from orebody and stoping footwall and major infrastructure; stockpiles, vent rises, escape-ways, declines and ancillary development are 50m.

The Rosebery crushing circuit consists of a Primary Jaw Crusher and a Secondary Cone Crusher. During Crushing the ore size is reduced from around 650mm to P80 of 20mm. The Grinding Circuit consists of 2 x Primary Ball Mills and 3 x Secondary Ball Mills.

Gravity gold is recovered from the grinding circuits using 2x Knelson Concentrators. Gold Concentrates are leached in an Intensive Leach Reactor (ILR). Then recovered from the pregnant leach solution by electrowinning and thereafter the gold sludge is smelted.

The recovery sequence for sulphide minerals in the Flotation Circuit is Chalcopyrite (Cu), Galena (Pb), Sphalerite (Zn). Payable gold and silver is recovered with the copper and lead concentrates.