A natural CO₂ reservoir system with a sandstone lithology in NW Hungary has been studied due to its similarities to a large saline reservoir formation that is widespread in the the Pannonian Basin (Central Europe) and is suggested to be one of the best candidates for industrial CO₂ storage. A range of analytical techniques has been used on core samples from CO₂-containing sandstone layers that represent a wide range of pressures (90–155 bar), temperatures (79–95°C) and pore fluid compositions (total dissolved solids between 18 000 and 50 700 mg l⁻¹) to identify the mineralogy and textural characteristics of the natural reservoir.

The only clear CO₂-related feature in the studied lithology was the occurrence of dawsonite (NaAlCO₃(OH)₂) in a close textural relationship with albite. This is in clear agreement with our geochemical modelling results, which also underline the presence of albite as a precondition for the crystallization of dawsonite at the given P–T–X conditions. Our results suggest that, at least in the Pannonian Basin, dawsonite may be an important mineral for the safe sequestration of industrial CO₂ in the subsurface.