The chemical, mineralogical, petrographic and textural characteristics of fly ashes from one fluidized-bed and two pulverized-fuel power stations in India, have been evaluated by a range of complementary methods, including optical and electron microscopies, laser granulometry, quantitative X-ray diffraction, X-ray fluorescence spectrometry and inductively-coupled plasma techniques. Mineralogical and geochemical analyses have also been carried out on the feed coals from the respective power stations, and the results were used to evaluate the changes produced during different combustion processes. Differences in particle size and shape for the ashes, and also differences in ash petrology and mineralogy, have been related to differences in the mineral matter of the feed coals, and to the milling characteristics and combustion temperatures in the different power plants. There is a potential of using these fly ashes as geoliner because of their fine texture and low permeability. Leaching tests have also been carried out on the fly ashes, as a basis for assessing the potential for adverse impacts on groundwater systems. The materials were blended with bentonite to decrease the permeability further. The major and trace element compositions of these ashes were determined. Most of the elements studied were leached in lower concentrations than averages for the same elements from European fly ashes. It is thus expected that these ashes will not provide significant source of additional contamination to permeating water if they are used with bentonite as geoliner material. (C) 2015 Elsevier B.V. All rights reserved.