The reduction of celestite concentrate to SrS using Al has been shown to be induced by mechanical activation. A thermodynamic appraisal showed that the reaction between SrSO(4) and Al is highly exothermic and should be self-sustaining. XRD analyses showed that reaction started only after milling for an induction time of 30-35 min, after induction only product peaks were present. Increasing milling time up to 60 min had no significant effect other than refining the crystallite size. The aluminium product was not Al(2)O(3) as expected but mixed phases such as Sr(3)Al(32)O(51), SrAl(4)O(7) and SrAl(2)O(4) which were thought to be formed by an adventitious oxidation process. (C) 2010 Elsevier B.V. All rights reserved.