This paper reviews the feasibility of using low grade clay for developing geopolymer mortar by partially replacing conventional source material. The study intends to develop a framework for identification, classification and utilization of various clays and suggest suitable processing techniques to qualify for geopolymerization. The influence of source clay based on the reactivity of silica, physical, chemical and mineralogical characteristics on the properties of geopolymer mortar is extensively studied based on existing literature. Characteristics of clay after various treatment methods (calcining and lime treatment) are also reviewed so as to identify the extent of its effectiveness on geopolymers. Characteristics based on micro-structural studies such as energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) along with geotechnical characterization are reviewed. The paper highlights the significant characteristics of clay that is significant for geopolymerization and its implication on the properties of geopolymer mortar. The manifestation of geopolymer characteristics and its relation to crystallography and microstructure is explored to develop strategies for the qualification of clays. The influence of parameters such as alkali concentration and sodium silicate to sodium hydroxide ratio on compressive strength is presented. Based on the review, an attempt has been made to characterize different types of clay obtained from few sources in India, and a study has been conducted to assess the qualification technique proposed. © RILEM 2020.