Two main types of mineralisation are recognised at Blanket mine, namely disseminated sulphide replacement reefs (“DSR”) and quartz-filled reefs and shears.

DISSEMINATED SULPHIDE REPLACEMENT REEFS
DSRs host the best grades and comprise the bulk of the ore shoots. These zones have a silicified core with finely-disseminated arsenopyrite. Relatively high grades are found in a package of silicified biotite chlorite schist with irregular quartz stringers and disseminated and stringer arsenopyrite in the fabric planes. Due to lesser silicification, abundant biotite characterise the margins of these mineralised zones and as a result they have a lower gold content. Disseminated sulphide-replacement Mineral Deposits range up to 50 m in width with a strike of between 60 m and 90 m. Free-milling gold constitutes up to 50% of the total metal content with the remainder locked in the arsenopyrite. The ore is not refractory despite its association with arsenopyrite. Generally, plant recoveries in excess of 90% are achieved.

- QUARTZ-FILLED REEFS AND SHEARS
The second type of mineralisation is the quartz-filled reefs and shears. Two quartz shears are mined at the Blanket Mine: the Blanket Quartz Reef and the Eroica Reef. These reefs have long strikes, however, they are not uniformly mineralised. Continuous pay shoots of over 100 m on strike are not present. The Quartz Reef at the Blanket Mine has a surface strike of approximately 500 m, but economic mineralisation is restricted to three 90 m long shoots which were defined on surface by the early workers (AGS 2006). Quartzfilled reefs display a much wider grade range compared to the DSR deposits. On average, these shears are of a higher grade and are used in blending the ore to the mill. Dominant ore minerals are native gold and galena although arsenopyrite becomes more prevalent below the 470 m elevation.

Wall rock alteration typically comprises silica-pyrite-muscovite within a broader carbonate alteration halo. Quartz-carbonate altered rock forms the most commonly recognised alteration assemblage.

The deposits may have a vertical extent of up to 2 km, demonstrate extensive down-plunge continuity, and lack pronounced zoning. The ore mineralogy is dominated by gold, pyrite and arsenopyrite. Subordinate minerals such as galena, chalcopyrite, pyrrhotite, sphalerite, tellurides, scheelite, bismuth and stibnite also occur. Sulphide mineralogy commonly reflects the litho-geochemistry of the host rock with arsenopyrite being the most common sulphide mineral in metasedimentary host rocks and pyrite or pyrrhotite being more typical in metamorphosed igneous hosts. The gangue and alteration mineralogy is dominated by quartz and carbonate (ferroan dolomite, ankerite, siderite, calcite) with subordinate albite, fuchsite, sericite, muscovite, chlorite and tourmaline

Blanket Mine uses mining methods that are commonly employed and well-understood by greenstone belt miners who generally have to deal with steep shear- hosted to massive mineral deposits. Since the nature of the mineral deposits varies, the exact mining practices are tailored to suit the specific attributes of each particular mineral deposit.

The main mining methods utilised at Blanket are:-
• underhand stoping in the narrow mineral deposits; and
• long-hole stoping in the wider mineral deposits.

Stoping preparations in narrow orebodies (less than 3 m wide) begin by mining raises at 10 m intervals along the haulage. These are usually mined from the footwall of the orebody to 10 m above the haulage drive. The extreme end raises are equipped as ladder-ways while the rest have boxes constructed under them. In wider orebodies, draw points are mined instead of boxes.

The wider orebodies are mined using long-hole open stoping methods which produce bigger rock fragments than the conventional methods. At the end of these draw point crosscuts, draw point raises are pushed 10 m to the above coning level. The draw point cross cuts are also mined at 10 m intervals along the haulage.

Where the orebody widths are less than 12 m the haulage is mined in the footwall of the orebody with draw points mined at 10 m centre-to-centre intervals from the footwall Haulage to the hanging wall contact. Raises are then mined from the ends of these draw points to the coning level. The draw points are mined 3 m wide and 3 m high.

Just as in the narrower areas the extreme end raises are equipped as ladder-ways. In both cases, a sublevel drive is then mined off the central raise to connect all raises laterally. These raises, one central and two at the ends, are then mined from the cone drive connecting all levels above. Additional sublevels are cut between levels after which the orebody is fully developed and ready for stoping.

Stoping commences by slyping around the central raise, on the cone level to expose the footwall and hanging wall contacts and will continue in retreat fashion 5 m either side of this raise.

Coning will then commence by blasting into the slot taking the full width of the orebody. The cone progresses down to approximately 3 m above the main level. As soon as the coning retreats a safe distance from the slot raise, to ensure men are safe from the rocks falling from above, a new stope is commenced at the central raise on the level above. This process is repeated on the sublevels above until a sufficient number of stope faces are in production above the cones to provide the required production tonnage.

The Blanket gold Plant consists of a conventional crushing, milling and CIL, batch elution and smelting configuration with a current capacity of 40 ktpm. The crushing and milling circuits are designed to process RoM. However, the CIL and downstream circuits were designed to treat tailings dam material at a rate of about 110 ktpm (or 3,800 tonnes per day). More recently, historic tailings and RoM were treated in the CIL plant at a combined rate of approximately 100 ktpm to 120 ktpm. The tailings treatment was stopped about three years ago. The CIL is currently used exclusively for treatment of RoM at a rate of 30 ktpm to 35 ktpm. The retention time in the CIL circuit is as high as 72 hr as a result of the lower tonnage throughput.

The plant consists of the following circuits:-
- jaw crushing;
- cone crushing in closed circuit with a screen;
- primary rod mill in open circuit;
- ball mill in closed circuit with cyclones;
- gravity circuit;
- dewatering cyclones;
- CIL;
- combined elution and electrowinning;
- smelt house;
- carbon re-activation in a kiln;
- reagent make-up and dosing circuits; and
- water recycling and storage.

The ore is fed over 14" x 24" jaw crushers to reduce the top size from -300 mm to less than 80 mm. Tramp iron magnets (located ahead of the crushers) remove scrap iron before it enters the cone crushers. This is important as any iron products from underground will cause major damage to the crushers if allowed to enter the crusher bowl. The crushed ore is stored on a 900 tonne open stockpile from where material is fed to the cone crushers.

The rod mill feed bin live capacity is small which, in turn, requires that the crushers operate on a threeshift cycle to ensure that the rod mills have adequate feed for continuous operation. There are plans to install additional storage capacity which will result in reduced operating costs in the crushing circuit. The cone crushers can then operate for fewer hours at a higher throughput thereby reducing operating unit costs and introducing more flexibility.

There are three 6.5 ft. x 12 ft. rod mills which operate in parallel. Each feed belt has a mill feed mass meter?which is used to control and measure the mill feed rate. The foundations of the previous mills were in the?process of being demolished which leaves adequate space for future expansion.

Approximately 45% to 50% of the gold production is recovered as gravity gold. Concentrate from the Knelson Concentrators is stored and re-concentrated on a Gemini table every 24 hours with the tailings recycled back into the circuit. Gemini table concentrates go for direct smelting whilst the tailings are pumped to the classifying hydro cyclone. The Knelson Concentrator tails are pumped through cyclones, the underflow of which reports to the open-circuit regrind ball mill.

The product from the Knelson tails cyclone overflow and the regrind mill discharge is pumped into the CIL plant. The CIL consists of one pre-aeration tank and eight leach tanks where alkaline-cyanide leaching and simultaneous absorption of dissolved gold onto granular activated carbon takes place.

Oxygen generated from a pressure oxygen plant is added into the first CIL tank; liquid oxygen is also available in the event of the oxygen plant being out of circuit for maintenance or breakdowns. There is a TAC 1000 cyanide online analyser which measures and controls cyanide addition. This process control system, in conjunction with oxygen injection, has reduced cyanide consumption.

Elution of the gold from the loaded carbon and subsequent electro-winning is done on site. There are two 2.5 tonne elution columns which operate in parallel. The design of the columns is unique in that the elution and the electro-winning processes take place in the same pressurised vessel. The advantage of this is that there is no circulation of solution outside the vessel which requires heat exchangers for heating and cooling. The overall effect is that the system is very energy efficient and cost effective.

During electrowinning the gold is deposited on wire wool cathodes within the elution column,
and the loaded cathodes are removed on a planned cycle and acid-digested. The resultant gold solids from acid digestion and the re-dressed gold concentrate from Knelson Concentrators are smelted into bars. The granular activated carbon is kiln regenerated before it is recirculated back to the CIL section. Loaded carbon is not acid treated in an attempt to reduce reagent costs. Carbon reactivation has remained acceptable although the acid treatment can be re-introduced if required. The gold bullion, in the form of doré bars, is delivered, as required by Zimbabwean gold-mining law, to the Government-operated Fidelity for samplingand onward delivery to the Zimbabwe gold refinery.