Pyrrhotine-pentlandite ore textures: a mechanistic approach.

The kinetics and mechanisms of pentlandite, (Fe,Ni)₉S₈, exsolution from the monosulphide solid solution, (Fe,Ni)_1-xS, have been studied by synthesis and annealing experiments, and the results combined with compositional and textural evidence from pentlandite-pyrrhotite intergrowths from a variety of ore deposits in the Strathcona and Copper Cliff mines, Sudbury, Ontario. The formation of a sequence of textures depends on the initial Me:S ratio and annealing time: the heterogeneous nucleation of pentlandite starts at pyrrhotite grain boundaries, followed by the growth of these blebs to form rims, nucleation of blades en echelon and homogeneous nucleation of fine orientated pentlandite lamellae.-R.A.H.