The hydrogen and oxygen stable isotope composition (δ² H and δ¹⁸O values) of mineral hydration waters can give information on the environment of mineral formation. Here we present and validate an approach for the stable isotope analysis of mineral hydration waters based on coupling a thermogravimetric analyzer with a laserbased isotope ratio infrared spectroscopy instrument (Picarro L-2130i), which we abbreviate as TGA-IRIS. TGAIRIS generates δ² H and δ¹⁸O values of liquid water samples with precision for δ² H of ± 1.2‰, and for δ¹⁸O of ± 0.17‰. For hydration waters in goethite, precision for δ² H ranges from ± 0.3‰ to 1.6‰, and for δ¹⁸O ranges from ± 0.17‰ to 0.27‰. The ability of TGA-IRIS to generate detailed water yield data and δ2 H and δ¹⁸O values of water at varying temperatures allows for the differentiation of water in varying states of binding on mineral surfaces and within the mineral matrix. TGA-IRIS analyses of hydrogen isotopes in goethite yields δ² H values that reflect the hydrogen of the OH− phase in the mineral and are comparable to that made by IRMS and found in the literature. In contrast, δ¹⁸O values on goethite reflect the oxygen in OH− groups bound to Fe (Fe-OH group), and not the oxygen bound only to Fe (Fe-O group) in the mineral crystal lattice, and may not be comparable to literature δ¹⁸O values made by IRMS that reflect the total O in the mineral. TGA-IRIS presents the possibility to isotopically differentiate the various oxygen reservoirs in goethite, which may allow the mineral to be used as a single mineral geothermometer. TGA-IRIS measurements of hydration waters are likely to open new avenues and possibilities for research on hydrated minerals.