The self-heating heat release rate coefficient QA (J g(-1) min(-1)) for Ni- and Cu-concentrates and sulphide mixtures has been determined. The QA for the concentrates were higher than those of the sulphide mixtures. This difference in QA between the materials, for which the reaction causing self-heating is surmised to be the same, may be attributed to differences in specific heat capacity C-p, a steric effect, and in the case of the mixtures, a galvanic effect. The lack of clear relationship between QA and the energy of activation E-a suggests at least both be measured to characterize the self-heating of sulphide materials. (C) 2014 Elsevier Ltd. All rights reserved.