Geopolymers based on natural zeolite clinoptilolite and addition of up to 50% metakaolin were synthesized using binary sodium/potassium alkali activator. The influence of metakaolin addition was evaluated on apparent density, water absorption, relative mass loss after watering and microstructure (XRD) of the prepared geopolymers. The addition of metakaolin greatly influenced the physical and mechanical properties of the obtained geopolymers. Minimal/optimal metakaolin addition was estimated to 30% in the respect of sufficient strength (11 MPa) and the high price of metakaolin. The resulted geopolymer based on natural zeolite and metakaolin (30%) contained residual unreacted clinoptilolite which could be beneficial for properties of future geopolymer products. Potential applications of obtained geopolymer-clinoptilolite agglomerates are: waste or radioactive water decontamination, passive cooling systems, plasters in residential buildings, etc.