The characteristic features of heat-activated pore-formation of zeolite-containing rocks (ZR) and opoka in alkali compositions were examined. It was determined that the low-temperature pore-forming gas phase in the systems opoka + NaOH and ZR + NaOH is water vapor that formed during dehydration of hydrated sodium silicates. In the mix ZR + NaOH the second, higher-temperature source of water vapor was found to be hydrated silicate surfaces of amorphized post-zeolite components.