During pre-beneficiation, the RoM material is crushed, screened at various size fractions and washed. In the primary mineral processing line, the 18-110mm fraction passes through laser sorting and magnetic separation to remove the largest portion of coloured or magnetic impurities (eg. serpentine, sepiolites and other silicates), and then enters the main beneficiation stage, whereupon it either passes through camera sorting or a combination of dense media and magnetic separation stages depending on the desired chemistry of the kiln-feed magnesite.
The secondary mineral processing line is the latest development, after having spent many years in designing and testing. Its purpose is to exploit the 0-18mm RoM material fraction which, until recently, was being stockpiled for future use.
The 0-18mm fraction from the crushing and screening plant, as well as material from the old stockpiles, are passed through specially designed sieves (Grecco-Screens) to remove the currently unprocessable 0-4mm fraction and then are separated to 4-10 and 10-18mm.
The 4-10mm fraction passes through special magnets able to process fine-grained materials and a cyclone unit. The latter fraction goes through new generation optical sorters and then is sent for calcination. It is estimated that the old 0-18mm stockpiles alone contain more than 40m. tonnes RoM material, while the freshly generated 4-18mm fraction represents approximately 20% of the total mine recovery.
Overall, at Yerakini, GM has installed 15 optical sorters (11 laser and four camera sorters), two classifying units, four magnetic separation lines, a sink-float and two cyclone installations.