We studied the geological and technological features of altered pyroclastic rocks from the main Bentomine Kimolian Enterprises S.A. quarry, in the Prassa region on the northeastern part of the Kimolos island, Greece. Particular emphasis was given to a MOR-type (mordenite) zeolite-rich material, tuff, which also contains K-feldspars, opal-CT and clays (mainly smectite) according to X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS). Additionally, it was characterised by a relatively low SiO2 component (av. 70 wt%) compared to surrounding volcanic rocks. Mordenite crystals are alkali- (Na- and moreover K-) rich. According to trace-element discrimination diagrams (Zr/TiO2–Nb/Y), the protoliths of the mordenite-bearing tuffs could be trachyandesites, whereas Ti/Al–Eu/Eu* diagrams indicated a clear felsic affinity. Normalised REE patterns confirmed an expected negative Eu anomaly and a relative HREE depletion, whereas relevant multi-element diagrams indicated positive Cs, Rb, Th, Pb, U and Ta, negative Ba, P and Ti and compatible elements anomalies. The SSABET of the rocks reached a value of 63 m2/g. In that case, the CEC was measured to be 98 meq/100 g. The above data suggest that the industrial minerals exploited in the Prassa quarry show good capabilities for the development of new products for innovative industrial and daily uses.