Four samples of violarite, of compositions Fe0.20Ni2.72S4, Fe0.46Ni2.49S4. Fe0.73Ni2.26S4 and Fe0.97Ni1.96S4, were synthesised and characterised. Each sample was fractionated into four, with particle sizes of 125-90, 90-63, 63-45 and <45 mu m. The samples were ignited in a TG apparatus, and the effects of change in stoichiometry and particle size on the ignition temperature, and extent of oxidation at a specific temperature, determined. Samples of the ignited material were taken at various temperatures, and their properties examined using scanning electron microscopy, optical microscopy and electron probe microanalysis. The results enabled an ignition mechanism for violarite to be proposed.