[en] Thermal decomposition of two garnets of near end-member composition--almandine (Fe_2.85Mg_0.15)(Al_1.99)Si_2.99O₁₂ and pyrope (Mg_2.22Fe_0.47Ca_0.33)(Cr_0.11Fe_0.06Al_1.81)Si_2.98O₁₂--has been carried out in reducing atmosphere (forming gas: 10% of H₂ in N₂). High-temperature behavior of both samples was monitored using simultaneous thermogravimetry and differential scanning calorimetry. The decomposition of almandine and pyrope turned out to proceed at slightly different temperatures above 1000 degree sign C. Therefore, two series of samples were prepared based on the results of thermal analysis: almandine heated up to 950 deg. C, 1070 deg. C and 1200 deg. C, and pyrope heated up to 1000 deg. C, 1100 deg. C, 1125 deg. C and 1200 deg. C. The identification of the decomposition products was performed by X-ray powder diffraction and Moessbauer spectroscopy. The common feature of the decomposition of both garnets is the presence of metallic iron and spinel phase, while the other products include fayalite, cristobalite, and cordierite for almandine; and enstatite and anorthite for pyrope. The formation of this last component was enabled due to Ca content in pyrope.