Vermicular kaolinite relics in fly ash derived from Bokaro and Jharia coals (Jharkhand, India)

Abstract During a study of fly ash from two pulverized fuel power plants (Bokaro and Chandrapura) burning coal from the Bokaro Coalfield in Jharkand state, India, glassy and vermicular mineral forms were found associated with the char. A combination of optical microscopy, XRD, SEM/EDS, and XRF analysis has shown that this morphotype, reported here for the first time, originated from kaolinite that expanded during heating inside the furnace chamber under relatively low combustion temperatures. The morphotype has an internal structure that resembles the fanning-out structure formed during vermicular kaolinite development.