Thermal behavior of three copper molybdates, lindgrenite, Cu 3 (MoO 4 ) 2 (OH) 2 , szenicsite Cu 3 (MoO 4 )(OH) 4 , and cupromolybdite, Cu 3 O(MoO 4 ) 2 , has been studied by high-temperature X-ray powder diffraction in the temperature range of 25–900 °C. The decomposition of lindgrenite and formation of cupromolybdite were observed at T > 325 °C according to the reaction: Cu 3 (MoO 4 ) 2 (OH) 2 → Cu 3 O(MoO 4 ) 2 + H 2 O. Szenicsite decomposes to cupromolybdite and tenorite at T > 350 °C according to the reaction: 2Cu 3 (MoO 4 )(OH) 4 → Cu 3 O(MoO 4 ) 2 + 3CuO + 2H 2 ↑. Cupromolybdite is stable up to 825 °C. The thermal expansion of lindgrenite, szenicsite and cupromolybdite is strongly an
