The Diavik Diamond Mine processes up to 2 million tonnes of ore annually.
Separating diamonds from the kimberlite host rock is a non-chemical, gravity-based process which relies on the diamonds' heavier weight to separate them from waste rock.
At the beginning of this process, diamond-bearing kimberlite ore is trucked to a storage area outside the process plant. A primary sizer reduces the ore before it enters the plant where it is mixed with water and crushed to less than 30 millimetres. The ore is then conveyed to the dense medium separation circuit. Here fine grained, heavy and magnetic ferro-silicon (FeSi) sand is added to the crushed ore and water mixture. The FeSi magnifies the gravity effect and enhances diamond and other heavy mineral separation. A large magnet recovers the FeSi, which is recycled. Water is also recycled.
The less dense waste kimberlite fraction is directed to the processed kimberlite containment (PKC) area for permanent storage. The heavy mineral concentrate (containing diamonds, garnet, diopside, olivine, and spinel) is conveyed to the recovery circuit.
In the recovery building, the diamonds are separated from the waste heavy minerals using X-rays to trigger a unique characteristic of diamonds. Diamonds glow under this kind of light, and photo-electric sensors direct strategically placed air blasts to blow the diamonds off the conveyor belt into diamond collection receptacles. Waste minerals are reprocessed and directed to the PKC. The diamonds are then shipped to the Diavik product splitting facility in Yellowknife where they are cleaned using chemicals, divided 60/40 between the joint venture partners (Rio Tinto and Dominion Diamond Corporation) and undergo evaluation, for government royalty purposes.
Processed Kimberlite Containment (PKC)
Despite being a high grade deposit, the diamonds represent approximately one part per million of the host kimberlite rock. Once this small fraction of diamonds is removed, the remaining kimberlite is placed in the Processed Kimberlite Containment area (PKC). Constructed in a natural valley in the centre of East Island, the PKC is bounded by dams constructed at either end.
At the completion of mining, this PKC area will be approximately 1 kilometre long and 1.3 kilometres wide and contain up to 40 metres of processed kimberlite. The PKC will be covered with waste rock to seal it safely forever.