The compound CuHgPS, crystallizes in the orthorhombic system, space group Pna2, (No. 33), Z = 4, with lattice paraorneten a = 12.660(3), b = 7.3498( 7), c = 6.0943(4) A, and Scale = 4.96 g/cm3. The title compound is stable in air and moisture and behaves as a semiconductor. The crystal structure consists of discrete tetrahedral PS43-anions joined together by Cu' and H?' cations. The arrangement of the sulfur atoms is approximately hexagonal close-packed in which P, Cu, and Hg occupy tetrahedral sites. The PS,, HgS,, and CuS4 tetrahedra are slightly distorted with mean distances d(P-S) = 2.055, d(Hg-S) = 2.524, and d(Cu-S) = 2.320 A, and 8% of the Hg atoms were found to be disordered, occupying interstitial tetrahedral sites. The title compound is isotypic to AgZnPS, and can be considered to be a defect structure of Enargite (Cu3AsS4), which is a substitution derivative of the Wurtzite (ZnS) structure. The CuHgPS, Vibrational spectrum has been recorded. The internal modes experimentally observed are in accord with the factor group prediction. A tentative assignment of the vibrational frequencies is proposed. 6.0943(4) A, V = 567.1 A". The anisotropic temperature factor is of the following form: exp [-273 (Ull/?a'* + ... + 2Ul3h/a*c')]. 'Defect positions, see text; site occupancies: Hgl 1, 0.920(2): Hg12, 0.080 (reset). 'Arbitrary fixed.