An international network of diamond buyers and suppliers on Thursday advised its members to boycott diamonds from Zimbabwe’s Marange fields, threatening to expel and blacklist anyone who violated the ban on trading in gems from the controversial area... The warning came as the diamond industry watchdog allowed Zimbabwe to auction 900 000 carats of more than 4.5 million carats of stockpiled gems from the controversial Marange fields... According to Rapaport,...there was no guarantee that Marange diamonds with KP certification are free of human rights violations... The KP had since last November banned exports of Marange diamonds, citing human rights abuses by security forces guarding the mines. It lifted the ban last month...