The degrees of decrepitation of a limestone and of a dolomite were determined by an industrially accepted procedure called the Pilkington test, and by a TG method. A good correlation in decrepitation trend with change in particle size between the two methods was apparent for the dolomite, and the maximum degree of decrepitation was found to be in the 180-250 mum (60-80 mesh) fraction by both methods. The correlation was less evident for the limestone, and the change in degree of decrepitation with particle size was different for the two tests. The TG method gave much larger values for the degree of decrepitation relative to the Pilkington test, and so can be considered a more sensitive test.