The Mako Mine is situated in eastern Senegal within the prolific Birimian age “Kenieba Window” geological complex that hosts multiple world class gold mining operations in eastern Senegal and western Mali.

Gold mineralisation is hosted mainly within the Felsic Unit which is sandwiched between two basalt sheets and is associated with disseminated and veinlet pyrite, quartz-carbonate-chlorite alteration and veining and is typified by zones of bleaching and hydrothermal brecciation within both the felsic unit and part of the Lower Basalt Unit.

Mineralisation is contained within a kilometre of strike length and over true widths varying between 5 and 40 metres. Mineralisation remains open at depth and previous deep drill holes have already identified higher grade shoots beneath the base of the open pit which are subject to further exploration to more fully assess their potential to support underground mining operations.

The Petowal deposit is developed as an open pit mine by conventional methods of drilling, blasting, loading and hauling using standard industry equipment. Top hammers, down-the hole hammers or rotary drills are used for drilling and blasting, depending on the rock characteristics and the optimum blast hole size selected. Grade control is achieved through Reverse Circulation drilling (Coffey, 2015). Dieselpowered 120 tonne hydraulic excavators with 90 tonne (approximate) haul trucks are used us the primary loading and hauling equipment. The pit is mined at a maximum rate of 2.4 Mt of ore per annum, producing 74 million tonnes of waste rock over the Project lifetime (Toro Gold, 2015a). Staged development of the Mine Pit is required in order to maximise the grade of the initial plant feed, minimise waste pre-stripping and fulfil the requirement for consistent total material movement. Stage 1, Stage 2 and Stage 3 are located on the foot wall side of the pit, with Stage 1 located to the south, Stage 2 extending Stage 1 to the north and Stage 3 extending the footwall side of the pit to the final extents of the Mine Pit. Stage 4 extends the southern half of the pit to the west and to full depth, with Stage 5 extending the northern half of the pit to the west and final depth (Coffey, 2015).

The Mine Pit intersecting predominantly fresh rock material. Five metre benches are used in the Mine Pit for mining the ore zone and 10 metre high benches for the waste rock zones.

Blasting is conducted where the ore and/or waste rock is too hard for an excavator to dig efficiently. Blasting is conducted daily, during the daytime, and will typically occur during shift changes or meal breaks.

Drill and blast procedures and designs will be prepared by blasting specialists to ensure:

Drill and blast procedures and designs are prepared by blasting specialists to ensure:
- Safety of the mine workforce and surrounding local population;
- Control of flyrock; and
- Noise / vibration control, e.g. through regular timing of blasting.

Following blasting, the ore is loaded and hauled out of the Mine Pit along the haul roads to the ROM ore stockpile area for processing. The waste rock is loaded and hauled out of the pit to the WRD or to facilities requiring waste rock for construction.

The carbon in leach processing plant has 2.3Mtpa of capacity and comprises a crushing circuit, an 8.5MW SAG Mill and gold extraction circuit.

Run of Mine Pad and Crushing
Haul trucks will deliver ore directly from the Mine Pit to the ROM Pad.

The ROM Pad will be used to provide a buffer between the mine and the Process Plant. The ROM stockpile will allow blending of ore feed stocks, and will ensure a consistent feed type and feed rate to the Process Plant. ROM ore will be loaded into the crushing circuit feed bin (ROM bin) by a front end loader.

Processing activities will be conducted on a 24 hour, seven days a week and 52 week a year basis.

Primary Crushing and Reclaim
ROM ore will be drawn from the ROM bin at a controlled rate and will discharge onto the primary static grizzly. Grizzly oversize material will report to the jaw crusher and will be crushed. Crusher product and grizzly undersize will discharge onto the crushing screen feed conveyor which will discharge onto a vibrating screen.

The crushed material will be sized on the screen into three size fractions and will undergo secondary crushing for further size reduction where required. Crushed ore will be fed via the SAG mill feed conveyor directly to the grinding circuit. Quicklime, used for pH control in the leach circuit, will be metered directly onto the mill feed conveyor from the lime silo. There will also be a secondary crusher strategy on standby to provide continuity in plant production and offset any downtime associated with crusher liner change-outs (Toro Gold, 2015a).

Dust extraction will be provided at transfer points with dust periodically discharged to the adjacent conveyor belts.

Grinding and Classification
Crushed ore will be milled to achieve the required size for effective gold and silver5 recovery. The grinding circuit will consist of a SAG mill in closed circuit with a pebble crusher and hydrocyclones.

Crushed ore will be fed directly to the SAG mill and process water will be added to the SAG mill to achieve the correct milling density. The SAG mill will discharge to the pebble dewatering screen and oversize material will discharge onto a series of recycle conveyors. Tramp metal will be removed from the pebble stream by a magnet. The pebbles will be crushed by the pebble crusher and will discharge onto the SAG mill feed conveyor and be fed back to the SAG mill.

The pebble dewatering screen undersize will gravitate to the mill discharge hopper, be diluted with process water and pumped to the classifying hydrocyclone cluster.

Processing operations are completed via the use of an industry standard “Carbon in Leach” plant comprising of a crushing circuit, an 8.5MW SAG Mill and gold extraction circuit prior to discharge to a lined tailings facility via a cyanide destruct circuit. The processing facility is anticipated to achieve average life of mine gold recoveries of approximately 89.6 per cent from a target grind of P(80) 125µm.

The overall process is summarised as follows (Toro Gold, 2015b):

- Primary jaw crushing and partial secondary cone crushing of ROM ore to produce a crushed product size of 80% passing (P80) 143 mm;
- A crushed ore surge bin and overflow dead stockpile with reclaim of crushed ore from the surge bin;
- Single stage SAG milling in closed circuit with a pebble crusher and hydrocyclones to produce an 80% passing 125 micron grind size;
- Pre-leach thickening to increase the slurry density feeding the CIL circuit to minimise CIL tankage, improve slurry m ........