The vaporization behaviour of barium silicate has been studied by mass spectrometric measurements. A new, previously unreported species has been identified in the gas phase BaSiO3(g). The thermodynamic functions of this substance, in the temperature range 298.15 K to 3000 K, have been obtained by Density Functional Theory (DFT) calculations. By combining the thermodynamic functions with the enthalpy of formation, obtained with the "second law" enthalpy of sublimation, the formation properties of BaSiO3(g) have been calculated.