Tenders were expected to be invited this week for the bulk sampling programme that forms part of a study into the economic feasibility of mining the Merensky reef as part of a potential future expansion drive at Northam Platinum’s new Booysendal mine, where only upper group two (UG2) reef is currently being mined.

The prefeasibility study is aimed at proving that the narrower Merensky reef, originally earmarked for conventional mining, can be mined using the same mechanised bord-and-pillar mining method that is being successfully implemented on the UG2 horizon, and that the bulk sample can pass the metallurgical tests, given that the Merensky material will be of lower grade.

“We need to ensure that we can still get high recoveries against a lower-grade product by designing for the dilution,” Northam Platinum CEO Paul Dunne explained to Mining Weekly.

Mining the UG2 reef using the mechanised bord-and-pillar method has delivered a world-class safety performance, which Northam would like to see replicated on the Merensky horizon, should the proposed new project be given the go-ahead.

“The biggest safety differentiator is without question the mining method,” Dunne said.

Booysendal’s UG2 operation is expected to be producing at a rate of 160 000 oz/y before the end of 2015 and Northam management sees merit in the proposed Merensky project benefiting from the UG2 mine’s same fleet of equipment and same skills sets.

Although the wider UG2 reef lends itself to the mechanised mining method more than the narrower Merensky reef, Northam does not believe that the Merensky reef should be mined conventionally.

“We think we should keep the mining methods consistent and we believe we can do that by accepting dilution on the Merensky. If the metal-lurgists know what’s coming, they can design the plant accordingly. “So that’s our preferred route – mechanised mining producing a high volume and lower-grade product,” Dunne added.

The site demarcated for the bulk sampling and potential boxcut is close to one of several historical adits developed by geological pioneer Hans Merensky, who discovered platinum nearby nearly 90 years ago.

“We identified those historical adits when we built the UG2 mine here and we aim to preserve them,” Northam Platinum project manager Rene Rautenbach added.