The crystal structure of chloroxiphite, Pb 3 CuO 2 (OH) 2 Cl 2 , from Merehead Quarry (monoclinic, P2 1 /m, a = 6.6972(8), b = 5.7538(5), c = 10.4686(14) Å , b = 97.747(10)º, V = 399.72(8) Å 3 ) has been refined to R 1 = 0.041. The structure contains three symmetrically unique Pb sites and one Cu site. The strong distortion of the Pb 2+ coordination polyhedra is due to the stereoactivity of the s 2 lone electron pairs on the Pb 2+ cations. The Cu-site is coordinated by four OH À groups to form an almost planar Cu(OH) 4 square that is complemented by two apical Cl À anions, forming an elongated [Cu(OH) 4 Cl 2 ] octahedron. Because of the large size and variability of coordination polyhedra around Pb 2+ cations and the strength of the MeÀO bonds in comparison to the MeÀCl bonds (Me = metal), it is convenient to describe the structure of chloroxiphite in terms of oxocentred OPb 4 tetrahedra. The O1 atom is tetrahedrally coordinated by four Pb 2+ cations forming relatively short and strong OÀPb bonds. The OPb 4 tetrahedra link together via common edges to form [O 2 Pb 3 ] 2+ double chains. The difference between chloroxiphite and other natural oxyhalides is the presence of Cu 2+ cations which form an independent structural unit that links to units formed by OPb 4 tetrahedra. In this sense, chloroxiphite can be considered as a modular structure consisting of both strong cation-and anion-centred units.