The uptake of nickel into the lattice of pyrrhotite, Fel_oS has been studied experimentally in the temperature range 200 DC to 760 DC. Nickel from both aqueous solutions and salt melts diffuses rapidly into the sulphide lattice with ,an accompanying rel~ase of iron into the solution or melt. The rate of uptake of nickel and its diffusion into the sulphide lattice have been followed ,by optical microscopy and by analysis with an electron probe microanalyser._x000D_
Some geological consequences of this phenomenon affecting the distribution of nickel in rocks associated with nickel-iron sulphide ores are discussed.