Cement clinker produced using a high sulfur petroleum coke fuel has been analysed to determine the identity of the sulfate-containing phases. Quantitative X-ray diffraction methods were used in conjunction with extraction procedures to concentrate or extract the sulfate phases. The minerals of interest were anhydrite (CaSO4), aphthitalite (3K(2)SO(4).Na2SO4), arcanite (K2SO4), calcium langbeinite (K2SO4.2CaSO(4)) and thenardite (Na2SO4). Overall sulfur content of the clinker increased in proportion with the amount of sulfur in the fuel. The clinker produced using the high sulfur fuel was found to contain a significantly increased concentration of aphthitalite but a reduced amount of thenardite. Comparison of the experimental results with theoretical predictions based on the Bogue formulae shows differences in respect of calcium langbeinite, which is not detected in the clinker, and thenardite, which is detected. (C) 2004 Society of Chemical Industry.