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.

CdS is composed of a number of underground and open pit operations. The southern portion of this mining complex is referred to as CdS I while the central portion (formerly known as São Bento) has been renamed CdS II and northern portion is called CdS III.

CdS I includes one underground operation and a number of individual open pit operations. CdS II includes one active underground operation (formerly known as the São Bento Mine).


The mining method for CdS I is sub-level stoping. Each panel consists of three levels, with secondary development of 300m from the cross cut in a north-east direction and 300m from cross cut in a south-west direction. The stopes are 15m in height. Some of the mining sequence is bottom/up, though all of CdS I is being converted to top/down sequences. According to geotechnical guidance, a sill pillar of 4m in height is designed between panels, and 4m rib pillars are used each 30m along the strike. The blast drilling for stopes is executed via fan drilling in ascending and descending directions. The loading and hauling operations are performed by with 8t front-end loaders and 30t articulated trucks, at an approximate rate as of 1,500tpd.

There are two metallurgical plants in CdS: the heap-leach plant for the oxide ore and the sulphide plant.

The sulphide process consists of crushing, grinding and gravity concentration, flotation, thickening, acidulation, pressure oxidation (POX autoclave), CCD (counter current decantation), CIL extraction, elution, neutralisation, electro-winning and tailings disposal. The plant and POX circuit have a capacity as of 600ktpy.

The heap-leaching process consist of crushing, agglomeration, stacking, leaching, adsorption, elution and electro-winning.