Four important deposit types have so far been recognized on the Mana property. The WonaKona deposit is hosted in relatively wide corridors of silicification with disseminated mineralization hosted in a sheared package of alternating fine grained metasediments and metavolcanics. At Yaho, the mineralization is associated with a strongly sericitized arenite, locally conglomeratic located within a wider deformation zone affecting metavolcanics and other fine grained sediments. The three southern deposits (Nyafé, Fobiri and Fofina) are hosted in dominantly sheared and silicified volcanic rocks hosted within quartz rich veins. These veins tend to be richer but narrower. Finally, the newly discovered Siou Zone is composed of a series of shear zones hosting free-gold bearing quartz veins located along a contact between a sedimentary sequence and a felsic intrusive.

The Wona-Kona mineralization occurs as disseminated pyrite and arsenopyrite in highly deformed and silicified meta-sedimentary of meta-volcano-sedimentary rocks. Locally, silicification is so intense as to form massive quartzitic bodies, which are commonly preserved within the saprolitic horizon. In some extreme cases blasting is necessary to mine within the saprolite horizon.

The mineralization at Nyafé, Fofina and Fobiri is also associated to pyrite and arsenopyrite disseminated on the edge of millimetric veinlets of microcrystalline grey quartz. Folded carbonate veinlets cross the mineralization.

Disseminated pyrite and arsenopyrite is omnipresent throughout the sericitized arenite which hosts the Yaho Zone but higher percentages are observed within four separate zones which also hosts the better gold grades. Gold values are consistently anomalous throughout the entire host unit (above 100 ppb). The delineated subparallel gold zones within the arenite can measure more than 50 meters thick, sometimes accounting for more than 50% of the entire host unit.

The mineralization at Siou occurs at or near the contact between a sedimentary unit to the west and a granodioritic intrusive to the east where series of shear zones containing quartz veining and sericite alteration over thicknesses of 5 to 25 meters are observed (Figure 7). The Siou Zone and the Nine Zone vary from less than one meter to close to 20 meters in width, with an average of between 4 and 4.5 meters. The shear zones dip approximately 45 to 60 degrees to the east.

All mining operations are presently realized by open pit method. Like in many oxidized ore deposits, the Mana open pits have been exploited with a percentage of drill and blast.

The ore selectivity is done by assaying the mineralized zones along berm trench samples. The geologists are drawing sampling lines on berms that are sampled for every 1m of length. The vertical influence of these samples is for 2.5 meters. According to the assay results, the ore/waste contacts are drawn on berms and selective mining is done to separate what is defined as high grade ore, medium grade, low grade ore or marginal and waste material. Technicians are assigned to the follow-up of all of the mining operations.

The open pit walls, except for some local faults or shear zones, are very stable. The average designed pit slopes of Siou, Fofina, Wona and Kona vary from 20° to 42° in saprolite or oxide ore and from 50° to 52° in saprock, fresh rock or sulphide ore depending on the depth and design configuration.

ROM ore is loaded by a WA600 front end loader onto a static grizzly screen to handle slabby material. A rock breaker reduces the oversize material that remains on the static screen (625 X 665 mm). Fine material drops into a 150 tonne capacity ROM bin. The ore is then extracted from the bin by a primary apron feeder (1,524 mm X 7,000 mm) and fed to a vibrating scalper (1,500 mm X 4,000 mm) to further separate the fines. Coarse material from the scalper feeds directly into a 36" X 48" (950 mm X 1,250 mm) single toggle jaw crusher. The crusher produces a product with a P80=100 mm, at a rate of 400-500 wtph to allow for a 17 hour per day crushing operation.

The grinding circuit consists of a Semi Autogenous Grinding mill (SAG) in close circuit with a vibrating screen and a pebble crusher. The 7.92 meter diameter X 2.74 meter Allis Chalmers SAG is equipped with 2,387 KW variable speeds motor and operates between 10-15% ball charges depending on ore hardness. Variable speed control provides additional flexibility for processing of various ore types.

Cyclones overflow gravitates to a trash vibrating screen (Simplicity 1524 mm X 3658 mm) ahead of the leach tanks. Trash screen oversize reports to a holding tank and then transferred to the tailings pump box. Underflow reports to a Heath & Sherwood automatic sampler for feed assays and then flows to the CIL tanks. The CIL circuit consists of 9 Carbon In Leach (CIL) tanks. The first eight tanks have a live capacity of 1,588 m³ each. The last tank has a live capacity of 3,182 m³. The tanks are sized to provide 24-28 hour residence time depending on throughput. Carbon concentration in the tanks is maintained between 12-15 g/l to maintain solution tail grades below 0.0015 mg/l. A cyanide distribution system composed of one mixing tank and one holding tank prepares a 10% cyanide solution. The solution can be pumped either to the grinding circuit or CIL tanks as required. The level of CN- into the leaching tanks is maintained around 125-180ppm depending on ore types. Oxygen is supplied by blowing air into the tanks at up to 2,000 m3 /h total. Hydrogen peroxide is also available if higher dissolved oxygen (DO) level is required into the CIL tanks. Each tank is fitted with mechanically swept wedge wire screen to retain the carbon. All tanks are fitted with bypass facilities to allow any tank to be removed from service for agitator or screen maintenance. Carbon enters the circuit at CIL tank #9 and advances counter-current to the slurry flow by pumping slurry, with a recessed impeller pump, from CIL tank #9 to CIL tank #8 as so forth. The carbon is retained by a screen and gravitates into tank #8 while the slurry flows back to tank #9. This counter-current process is repeated until the carbon eventually reach CIL tank #1. A recessed impeller pump is then used to transfer slurry and loaded carbon to the loaded carbon screen (Simplicity 1,219 mm X 2,438 mm) mounted above the carbon elution and stripping plant. The loaded carbon, reporting as screen oversize, gravitates to the acid wash column and the screen undersize slurry returns to CIL tank #1. Discharge from the last tank is directed to the tailings pump box via a vibrating carbon safety screen (Simplicity 1,524 mm X 3,658 mm) design to recover any carbon leaking from the last CIL leaching tank. Carbon recovered on the safety screen is directed to the CIL spillage sumps and pumped back to the CIL tanks. Tailings going through the screen are directed to a Heath & Sherwood automatic sampler for tail assays and then flow to the tailings pump box.

Loaded carbon is received into a 4 tonne – 8 m3 acid wash tank. A 3-5% hydrochloric acid (HCL) solution is prepared and circulates in an up-flow manner through the carbon bed for approximately 3 hours. The acid solution is then neutralized with caustic and the carbon rise (3 bed volume) with fresh water. Acid wash is necessary to remove carbonate scale (CO3) that builds on the activated carbon during the adsorption process which fouls the carbon’s adsorption properties. Acid washed loaded carbon is then pumped from the acid tank to the two elution columns.

Fresh strip solution is prepared prior to stripping each new batch of carbon. Sodium hydroxide and cyanide solution is pumped into the strip solution tank and mixed with raw water to the required concentrations of cyanide (0.15% w/v) and caustic soda (2.0% w/v) at pH> 12.0. The pressurized Zadra strip utilizes 30-36 bed volume of a circulated 130 °C solution at a pressure of 400 kpa to strip the carbon. The barren strip solution is indirectly heated via a diesel-fired hot glycol (33% w/v) heater and pumped in an up flow manner through the carbon inside the 2 tonne strip column. The pregnant strip solution exiting the top of the column is routed to the electro winning cells, where the precious metals are electro-chemically precipitated into a sludge form at the cathodes. The strip solution is then routed back to the solution storage tank. The strip solution recirculates continuously for 8 -12 hours until the gold level of the strip solution reaches 2-8 g/t Au. At that stage the barren carbon level is less than 80 g Au/t carbon. Once the first column is being stripped, automatic valves are switched to start a new batch on the second 2 tonnes carbon loaded column. Approximately 4 tonnes of loaded carbon is stripped every day.

After completion of the elution process, the barren carbon is transferred from the elution column to a dewatering screen prior to entering the feed hopper of the carbon regeneration kiln. The kiln can regenerate approximately 150 kg/h of barren carbon. As the carbon is contaminated with organic species, the organics foul the carbon and cause the gold and silver adsorption rate to slow and decrease the metal loading capacity of the carbon. This action is corrected by heating the carbon to 625°C in a slightly oxidizing atmosphere which burns the organics from the carbon. The carbon is held at this temperature for about 15 minutes to allow regeneration to occur. Barren carbon is then stored in a holding tank prior to being pumped to a single deck carbon sizing screen (Simplicity 1,219 mm X 2,438 mm) above CIL#9. The carbon sizing screen is fitted with a 0.8 mm square aperture polyurethane decks. Oversize carbon reports to CIL tanks and the fine carbon is stored, filtered and bagged ready to be shipped to recover residual gold left into the fines.

The two 75 ft³ electro winning cells supplied by Summit Valley are designed to treat approximately 12.0 m3 /h of pregnant solution each. Individual cell electrical power is supplied by a local rectifier with the range of 2.7-3.3 volts and 800 amps output. Fumes generated during electro winning are removed via a local exhaust system. Gold is recovered as sludge from the stainless steel mesh cathodes. Sludge is washed from the cathodes with high pressure washer and pumped into a holding tank prior to feed a 85 liter Siemens’ press-filter; gold is then recovered as a filtered-cake and burned off in an electrical calcine oven. The dried gold cake is then smelted with fluxes in a diesel-fired furnace to produce Doré bars. Fumes generated during the smelting is recovered and processed through a wet dust collector to recover fine particles and followed by an exhaust fan to remove heat and fumes.