Talnakhite is a Cu-Fe sulphide first reported by Bud’ko and Kulagov (1963) as having a composition of CuFeS1.8 and a cubic unit cell with a = 5.28 Å. They proposed that this was the natural equivalent of synthetic high-temperature chalcopyrite (a = 5.26 Å). Subsequent work by Genkin et al. (1966) and Cabri (1967) suggested that talnakhite has a larger cubic unit cell with a = 10.6 Å, similar to that of synthetic β-phase (Hiller and Probsthain, 1956). This study shows talnakhite to have a cell with a = 10.593 Å, space group 143m, and a partially-ordered structure which is consistent with both the β-phase and the metal-rich stoichiometric composition of Cu18Fe16S32 (Cabri and Harris, 1971).