CdS is located in the eastern part of the lower to middle greenschist facies archaean Rio das Velhas greenstone belt. The CdS I, II and III gold deposits and associated targets are located in a gold trend that extends for about 14km in a north-easterly direction, from Grota Funda (CdS I areas) in the south to Jambeiro (CdS III areas) in the north. The main gold targets and deposits are distributed over three trends, namely the CdS trend, the Donana Trend and the Cristina Trend. CdS mineralisation occurs in a greenstone belt geological environment, associated with quartz and sulphides (mainly arsenopyrite) in a structurally controlled corridor approximately 16 – 20km in strike length and about 500m vertical extent.

The CdS deposits consist of narrow north east/south-west elongated lenses of mineralisation dipping 60° to 70° south-east and plunging 20‚ to 30° north-east. CdS is an orogenic type deposit and comprises many hydrothermal lodes with quartz veins and low sulphide content disseminated in the wall rocks. The deposits are narrow, elongated and folded. In general, the mineralisation consists of sericitic zones and quartz veinlets.

The gold occurs as free and coarse gold and also as microscopic or sub-microscopic inclusions in arsenopyrite and sometimes iron-antinomy sulphide berthierite (FeSb2 S4). Other typical sulphide minerals are pyrrhotite, pyrite and chalcopyrite.

The underground mining method for CdS is sub-level stoping. Each panel consists of three levels with secondary development drives approximately 300m along strike in the northeast-southwest direction and cross-cuts of 300m in a southwest direction. The stopes are 15m high and use a top-down mining sequence. Geotechnical parameters require that sill pillars are 4 to 6m high, and rib pillars 4m wide. Stope drilling is drilled upwards using a fan design. The load and haul operations are performed by 8t front-end loaders and 30t articulated trucks, at an approximate rate of 2,500tpd, including ore from stopes and secondary development.

The open pit operation uses conventional bench mining, with 8m individual benches and 3.2m berms.

There are two metallurgical plants in CdS: the heap leach plant for oxide ore and the sulphide plant. The sulphide process consists of crushing, grinding and gravity concentration, flotation, thickening, pressure oxidation (POX autoclave), CIL extraction, elution, neutralisation, electrowinning and tailings disposal. The plant and POX circuit have a capacity of 600ktpa.

The heap leaching process consists of crushing, agglomeration, stacking, leaching, adsorption, elution and electrowinning, with capacity of 900ktpa.