Grain size analysis of 48 samples of Isalni(a power plant lignite ash revealed a mixture of three populations, each of them showing best fit to Weibull distribution with smallest size (x(0)) 40, 350 and 740 mum, mean size (x(m)) 163, 506 and 1068 mum, exponent (alpha) 1.42, 2.31 and 0.84, and participation to the whole mass with (p) 49, 23 and 28%, respectively. The fine population originates, according to the "two phase model of coal", from the mineral, the coarse, from the maceral pseudo-phase, while the middle fraction is presumably formed from extraneous minerals. Other three samples taken from the same power plant twenty years later could be resolved alike in three populations, with x(0) and x(m) shifted to smaller sizes. Concentrations of Na and Ca are evenly distributed among size classes, concentrations of K, Mg, Al, Fe, Ti and P are decreasing with particle size, while the concentration of S and C increases from the smallest to the largest size class 5 and 10 times, respectively, due to the mainly organic origin of these elements. (C) 2001 Elsevier Science Ltd. All rights reserved.