The first stage of the Albion Process™ is fine grinding of the concentrate, which introduces a high degree of strain into the sulphide mineral lattice. The number of grain boundary fractures in the mineral increases, enabling leaching under atmospheric conditions. Fine grinding is carried out in energy efficient IsaMills™.
Fine grinding also prevents passivation of the leaching mineral by products of the leach reaction. Passivation is normally complete once the precipitated layer is 2 to 3 μm thick. Ultrafine grinding of a mineral to a particle size of 80% passing 10 to 12 μm will prevent passivation, as the leaching mineral will disintegrate prior to the precipitate layer becoming thick enough to passivate the mineral.