A comprehensive characterisation of fly ash from Bokaro Thermal Power Plant, Jharkhand, India has been carried out for creating utilisation potential of the ash. As received fly ash, was size fractionated and the fractions were characterised. The non-magnetic and magnetic fractions of ash have been analysed in terms of their morphological, mineralogical features and physico-chemical properties. The results of such analysis reveal that there is a striking difference in the features and properties of the coarser and finer particles. The coarser fractions of the non-magnetic component seem to contain high percentage of char and semicoked/coked carbonaceous particles. The percentage of char albeit the carbon content decreases with decrease in size of the particles. The particles of the finer fractions have more spheroidal character than the coarser ones. The nonmagnetic components essentially contain quartz and mullite as the main mineral phases. The magnetic component differs from the non-magnetic ones in respect of shape, mineralogical composition and carbon content. These are much more spheroidal than the non-magnetic ones. The ferrospheres present in these components bear crystallites with different geometrical patterns clearly indicating a definite degree of variation in the crystallisation process. Such comprehensive characterisation leads to not only a definite direction about the uses of the various fractions of the ash, but also gives useful informations regarding the prevailing combustion process. (C) 2005 Elsevier B.V. All rights reserved.