"I know we are very close to signing a deal," he said. The NUM also represents the majority of workers -- 87 percent -- at African Rainbow Minerals' Modikwa mine, where it concluded wage negotiations in March, according to the company. The NUM, which remains the biggest union in gold, is seeking the right to be recognised at Harmony Gold Mining's largest mine, Kusasalethu, where the Amcu is the majority labour group. The union fell to 15 percent of employees, half of the threshold for recognition, according to spokeswoman Marian van der Walt. "We continue to engage with them, and they still enjoy the basic organisational rights at the mine." The claim for recognition is due to be heard today by the Commission for Conciliation, Mediation and Arbitration, Van der Walt said. Platinum Belt Founded 32 years ago and once South Africa's biggest labour union, the NUM has watched its influence decline as the Amcu gained a grip on the platinum belt northwest of Johannesburg.