The Rothsay Gold Mine is located within the Warriedar Greenstone gold belt, an Archaean sequence of mafic, ultra-mafic, meta-volcanic and sedimentary rocks folded in an anticlinal formation which plunges and strikes to the north-northwest with steeply dipping limbs.

The deposit is hosted in three discrete areas and within five individual shear zones. Woodley’s Shear (formerly A Shear). Woodley’s East and associated HW shears (formerly H Shear) occur to the east of the main Woodley’s Lode. Orient Shear (formerly B Shear) and Clyde and Clyde East Shears (formerly C and D Shears) occur in a second area further west and Miners Shear (formerly E Shear) occurs as an isolated shear in the north west.

The Woodley Shear is located at the contact between serpentinised peridotite and a porphyritic pyroxenite. The serpentinite forms the hanging wall unit. A sequence of mafic volcanic and sub-volcanic sills forms the hanging wall to the serpentinite.

The Woodley’s Shear is characterised by several generations of quartz veining with adjacent tremolite alteration. The early quartz phase is typically blue-black due to the partial replacement of alumina by chromium oxide. The shear zone is typically two to five metres thick and mineralisation does not typically occur outside the shear zone. The main gold mineralisation is associated with shear-hosted quartz veins of blue and white quartz of up to 3m thickness. The footwall porphyritic dolerite is relatively un ........

Longhole open stoping was selected as the mining method for Rothsay. Diluted stope shapes above the cut off grade were created. Stopes were then excluded from the Reserve by the following criteria:
- Isolated stopes or stoping areas which could not support access development
- Stopes which were in proximity to old workings and could not be mined

Operating and capital development were then designed to access the stoping levels every 15 vertical metres.

Rothsay is a vertical narrow orebody. Longhole top down stoping is a standard mining method for vertical narrow orebodies.

Sill pillars every four levels (60mV) and an allowance of 4.8m every 40m along strike (12%) in recovery loss for rib pillars were included in the model and stope shapes.

The assumptions used to determine the minable shapes was a minimum ore width of 1m wide plus the dilution on each wall of 0.5m. A 15mH x 10mL stope dimension was also applied to determine the mineable shapes above the cut-off grade. Level development is spaced every 15m resulting in stope heights of 12m from the backs to the floor of the level above.

Mining recovery factor of 83% was applied to account for planned and unplanned ore loss. This included a 5% loss for unplanned losses and a further 12% for planned losses (pillars).

A haulage decline, escape routes and ventilation decline/rises have been designed. Design methods are in-line with industry standards for eq ........

Regrind and Classification
The regrind circuit will consist of a single stage ball mill in closed circuit with a hydrocyclone cluster.

Flotation tailings will be directed to a high rate thickener to increase the density of the slurry prior to regrinding. Flocculant will be pumped to thickener feed and diluted (by a factor of ten) before addition. Clarified thickener overflow will gravitate to the leach thickener overflow tank.

Thickened underflow will be pumped to the regrind mill. The regrind mill will be a 2.85 (inside shell) x 4.5 (effective grinding length) overflow ball mill relocated from Andy Well. The mill will operate with the maximum ball load of 34% to maintain a motor power draw of 430 kW. Media addition to the mill will be via a ball loading kibble.

Slurry passing through the mill will flow into the Regrind Mill Discharge Hopper where it will be combined with the regrind gravity tails. Process water will be added to the hopper to achieve the correct density prior to being pumped to the Regrind Cyclones. The Regrind Cyclones will classify the ground slurry, with the cyclone overflow reporting to the each circuit and the cyclone underflow to the Regrind Mill for further regrinding. A portion of the cyclone underflow will report to the regrind gravity screen.

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