Thermodynamic data (ΔH, ΔS, ΔV) for fluid-independent chemical equilibria among minerals have been calibrated empirically in many studies. The calibration procedure involves first determining the pressures and temperatures of equilibration using thermobarometers applied to natural samples. Equilibria which operated in the same or nearby samples may then be calibrated by assuming a behavior consistent with heterogeneous chemical thermodynamics. Because of problems with thermobarometry, it has never been clear that thermodynamic data derived in this way carry meaning in a thermodynamic context. Whether such data behave according to established thermodynamic principles may be investigated using the calibrations of 43 fluid-independent equilibria among the minerals quartz, muscovite, biotite, garnet, and plagioclase reported in Hoisch (1991). Values (H, S, and V) for end member components in biotite (phlogopite, annite, eastonite, and siderophyllite) and muscovite (muscovite and MgAl-celadonite) were determined in the present study by applying multiple regression to the previously published reaction quantities ΔH, ΔS, and ΔV. The derived values compare favorably to those published in previous studies, even though different studies embedded different choices of activity models and different calibration methods. Also, values of ΔH, ΔS, and ΔV reconstituted from the derived data are very similar to the values published in Hoisch (1991). These results indicate that empirically calibrated thermodynamic data for mineral equilibria and mineral components carry meaning in a thermodynamic context.