The Ruashi ore body is a stratiform, sediment-hosted copper deposit (“SSC”) located in the Central African Copper belt. The Copper belt forms one of the world’s greatest metallogenic provinces containing over a third of the world’s cobalt reserves and a tenth of the world’s copper reserves. The Central African Copper belt is second only to the Chilean Porphyry belt in terms of copper endowment but lags significantly in terms of production.

The Ruashi copper-cobalt ore bodies are situated within a 24 km long by 2 km wide, northwest to southeast trending fold structure. The Lukuni-Ruashi Etoile trend consists of a recumbent, synclinal fold, Ruashi on the southern limb and Etoille on the northern limb. The flanks are made up of Roan rocks and the core by the Mines Group, all occurring to the southwest of a prominent regional northwest to southeast trending thrust fault. A local thrust fault dipping to the south, locates within the RAT formation immediately south of the Ruashi ore bodies. A listric fault-breccia pattern separates the ore bodies from one another.

Three ore bodies have been identified at the Ruashi Mine, namely Ruashi I, Ruashi II and Ruashi III.

Ruashi I, the largest of the three, is located in the northwest of the mining area. The lateral extent of Ruashi I measures approximately 900 m in a northwest to southeast direction and 350 m across strike. In cross-section, the oxide zone extends to approximately 130 m below surface, whilst sulphide mineralisation has been intersected to depths of more than 300 m below surface. The Ruashi I ore body terminates against a brecciated shear zone on the north-western and south-eastern edges of the pit.

Ruashi II is a smaller fragment, extending along strike for approximately 200 m and 250 m across strike. It terminates against listric shear zones to the north-west and south-east. Currently, a flat lying thrust fault terminates the ore body in depth. Exploration is planned to confirm the lack of, or existence of a mineralised ore body below the thrust fault. A large gap of approximately 200 m of brecciated Lower Kundelungu strata separates Ruashi II from Ruashi I.

Ruashi III occurs at the south-easterly end and has a strike length of approximately 650 m and a cross strike width of 200 m. Unlike Ruashi I and II, the copper orebody is buried by 30 m to 80 m of cover rocks. A HG cobalt zone or “cap” with low grade copper starts at a depth of approximately 12 m below surface in the west. Ruashi III is structurally controlled within a complex fold structure. The oxide zone extends to a depth of 300 m in the east. Drilling during the latter part of 2010 exposed malachite mineralization some 200 m beyond the previous eastern limits of the ore-body, down to depths of 300 m. Artisanal mining on Ruashi III has not been as extensive as at Ruashi I and II, and was restricted to the upper near surface cobalt zone 10 to 20 m below surface.

Oxide copper minerals at Ruashi include malachite, chrysocolla, native copper, cuprite, cornetite and azurite. Other oxide minerals include magnetite and specularite. The dominant cobalt mineral in the oxide zone is heterogenite. Trace quantities of oxidised uranium minerals have been observed but are very uncommon.

Chalcopyrite and diginite dominate the copper minerals in the sulphide zone (up to 96%). Bornite is found in minor quantities. Cobalt sulphides in the form of linnaeite and carrollite are irregularly distributed in intimate mixtures with the copper sulphides, with sporadic abnormal concentrations. Extremely high quantities of cobalt may occur in veins dominated by cobalto-calcite. Disseminated pyrite is found in all the formations and occurs as small amorphous masses in the grey RAT (Roches Argileuses Talceuse).

Abundant pyrite mineralization occurs in the graphitic shales of the SDS zone. Chalcocite together with malachite occurs below the water table in the transition zone as replacement rims on primary bornite and chalcopyrite sulphides. Cobalt sulphides generally decrease with depth beyond the transition zone.

Ruashi Mine is an open cast mining operation and the deposit is mined by conventional open-pit mining methods using truck and excavator combinations.

Ruashi I is largely mined out up to a depth of approximately 52 m below surface (1 240 amsl). The design extends another 28 m down to the 1 205 level. However, a southern pushback is planned to access additional ore at depth. The pit is accessed by a ramp from the north, with the north-western and south-eastern parts being serviced by ramps branching off from the existing northern ramp.

Ruashi II is the smallest of the three ore bodies. The design extends up a depth of 90 m below surface (1 195 amsl). The pit has a diameter of roughly 400 m on surface. A single ramp provides access to all the levels in both Pit II and Pit III. The current pit floor is 41 m below surface.

Ruashi II is the smallest of the three ore bodies. The design extends up a depth of 90 m below surface (1 195 amsl). The pit has a diameter of roughly 400 m on surface. A single ramp provides access to all the levels in both Pit II and Pit III. The current pit floor is 41 m below surface.

Ruashi III is the largest ore body with the highest overburden stripping requirement. The pit floor of phase I stripping is now at 25 m below surface and the BOMZ horizon containing HG cobalt ore is exposed in the northern portion of the pit. The pit has a designed depth of 190 m with the lowest bench on the 1 095 m elevation and is accessed by a dual ramp system. However, the poor geotechnical qualities of the weathered RAT unit on the southern pit walls preclude the presence of permanent ramps. The ramp configuration is largely a function of the separate mining stages on the southern and northern side of the pit.

The mining equipment is owned and maintained by MCK, the mining contractor. The majority of material can be loaded without drilling and blasting. Loading is carried out by diesel powered hydraulic excavators. Waste and ore is hauled by 40 t ADTs.

Reduction Plant (Crushing and Milling)
The primary crusher consists of a ramp for tipping of RoM ores, vibrating grizzly, a feed-bin, a jaw crusher and feeders for discharging material. Material from the primary crusher is discharged onto a stockpile. It is removed from the stockpile via 4 apron feeders and 2 conveyors located in a tunnel which then feeds the mill feed belt conveyor. The standby crushing plant which primarily serves as a back-up function, discharges directly to the mill feed belt conveyor.

The mill feed belt conveyor delivers the crushed ore to the Semi Autogeneous Grind (“SAG”) mill. Water is added to the mill. The milled ore then gravitates to the mill discharge sump. From the sump the mix is pumped to a bank of four cyclones (of which one is currently a stand by unit). The cyclone overflow from the mill circuit reports to the Pre-Leach-Thickener.

The power rating of the SAG mill is 1.2 MW and the 5 secondary ball mills each has a rating of 250 kW. Only three of these mills are in operation at any time with two mills as spare. The milling circuit capacity is 220 tph. The average grind is reported to be 65% -75 µm.

Ruashi Mining commenced stockpile mining operations in June 2005 for processing through the Ruashi Phase I oxide flotation concentrator plant. Phase I involved the construction of a concentrator plant to treat the oxide stockpiles that were left untreated by Union Minière and Gécamines with the concentrate being transported to the SX-EW facility owned by Sable Zinc in Zambia where copper cathode and cobalt carbonate were produced. Phase II of the project commenced in March 2007 and involved the development of the Ruashi Mine opencast orebody and the construction of an expanded crushing and milling section, the new acid leaching section and SX-EW plant for the production of copper cathode and cobalt hydroxide on site from ore mined from the Ruashi Mine orebody. Open-pit mining operations at the Ruashi Mine commenced in October 2007. Stockpile reserves were depleted and the Phase I concentrator plant was placed on care and maintenance in March 2009. All copper and cobalt have been produc ........