The heat capacity of natural chalcanthite (copper sulfate pentahydrate, CuSO4.5H2O) from the deposit Kosmurun has been measured by the method of low-temperature adiabatic calorimetry over the temperature range of (4.3-320) K. The identity of the mineral was proved by methods of XRD, EMPA, IR and Raman spectroscopy. The thermodynamic functions have been calculated based on the experimental data on the heat capacity. The lattice component of heat capacity below 20 K was extracted. The standard values of the heat capacity and entropy for natural chalcanthite are as follows: C degrees(p,m) = 288.0 +/- 0.4 J.mol (1) K (1), S degrees m = 295.2 +/- 0.8 J mol (1) K (1). (C) 2017 Elsevier Ltd.