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The behaviour of iron in ZnS has been studied through the effect of iron concentration on magnetic and electrical properties. Specimens containing iron in amounts varying from 0.09 to 16.16 atom per cent have been synthesized. These were found to be homogeneous by electron-probe microanalysis and under the reflecting microscope. At lower iron concentrations the synthetic and natural iron-bearing sphalerites are paramagnetic and their magnetic susceptibilities vary with the iron content in a linear manner. At higher iron concentrations these iron-bearing sphalerites become increasingly antiferromagnetic and their magnetic susceptibilities vary in a non-linear manner. The antiferromagnetic behaviour may be comparable to that observed in Mn-bearing ZnS and is probably the result of similar magnetic ordering of the substitutional iron. Electrical conduction for a natural iron-bearing sphalerite has been found to result from migration of low-mobility holes rather than by electrons. This observation is consistent with the mechanism known as d-band conduction, which attributes electrical current to the flow of holes in the d-bands of transition metals. This type of conduction is possible in iron-containing ZnS through the interaction of Fe+ with Fe2+, with the Fe3+ in either the tetrahedral or the octahedral position.

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Orthorhombic CuFe2S3 is weakly ferromagnetic. The magnetic susceptibilities of single-crystal and polycrystalline specimens have been determined at temperatures between 78 and 500 °K. A model is presented to explain the weak ferromagnetism.