The pozzolanic potentials of three non-thermally treated, nano-montmorillonite (NMt) dispersions were investigated by a new method involving the analysis of NMt/lime putty pastes via TGA/dTG and XRD crystallographic and semi-quantitative analysis. The criterion conceived was validated at eight days and eight months and was additionally verified via the Chapelle method. The inorganic NMt dispersion showed the most pronounced pozzolanic behaviour promoting Ca(OH) 2 consumption towards calcium silicate/aluminate hydrates formation and binding behaviour. The two organomodified NMt dispersions exhibited pozzolanicity increasing with time. The results can pave the way for advances in cement science and restoration mortars development for historical structures rehabilitation, where low CO 2-footprint, natural inorganic materials are a prerequisite.