The mineralogical content of coal mine waste consists primarily of inorganic compounds which can be converted into a metakaolin-based product under controlled activation conditions that is also a highly pozzolanic material. Activation temperatures ranging from 500 to 900 degrees C over 2 h retention time affect the mineralogy of coal mine waste, as well as the formation and evolution of the hydrated phases that form during the pozzolanic reaction. The hydrated phases formed during the pozzolanic reaction in the activated coal mine waste (ACMW)/Ca(OH)(2) system were C-S-H gels, stratlingite, tetracalcium aluminate hydrate, LDH compounds (phyllosilicate/carbonate) and monosulfoaluminate. Low temperatures (600 degrees C) favored the formation of LDH compounds and stratlingite; whereas monosulfoaluminate formed during the hydrated phase at higher temperatures (900 degrees C) during the first day of the pozzolanic reaction, and tetracalcium aluminate hydrate appeared as the dominant crystalline phase at 7 and 28 days. (C) 2014 Elsevier B.V. All rights reserved.