Quantitative X-ray diffractometry using a Rietveld-based computational method (SIROQUANT (TM)) has been carried out for a series of coal samples from the various Turkish mines. Standard proximate and ultimate analyses were carried out. Chemical compositions of the high-temperature ash (HTA) of coal samples were determined by X-ray fluorescence (XRF) spectrometry technique. Crystalline (mineral) matter and amorphous content of raw coal samples were estimated. The Ca, Si, Al, S and Fe concentrations are higher than those of the other major elements (Ti, Mn, Mg, Na, P, K) in the studied coal samples. The percentage of crystalline (mineral) matter for each sample varies from 16.5% to 36.1% of the coal samples. The minerals in the sampled coals consist mainly of quartz, clay minerals, calcite, pyrite, and gypsum. Percentages of crystalline (mineral) matter in ash content remarkably decrease for the Elbistan, Orhaneli, and Tufanbeyli lower-rank coals. (c) 2006 Elsevier B.V. All rights reserved.