JOHANNESBURG – Black Rock Mine on Wednesday said it was investigating an internal complaint of sexual harassment involving a manager and a female employee. The investigation was initiated after the National Union of Mineworkers (NUM) reported the matter to senior management last week. NUM said the alleged perpetrator should not continue to interact with other employees at the the Black Rock operation. The Assmang manganese ore mine in Norther Cape is 50%-owned by billionaire Patrice Motsepe's African Rainbow Minerals (ARM). Commenting on behalf of Assmang, ARM's head of investor relations Jongisa Magagula said the incident was being thoroughly investigated. "Yes the alleged sexual harassment incident was reported to management," Magagula said.