This dataset presents the amount of different magnesium carbonates under different conditions. Here, using batch reactor experiments and mineralogical characterization, we explored magnesite precipitation kinetics in chemically complex fluids whereby the impact of fluid acidity and alkalinity, NaCl, and MgO nanoparticles was investigated. The dataset was created within SECURe project (Subsurface Evaluation of CCS and Unconventional Risks) - https://www.securegeoenergy.eu/. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 764531