THE CRYSTAL-STRUCTURE OF OWENSITE, (BA,PB)(6)(CU,FE,NI)(25)S-27, A NEW MEMBER OF THE DJERFISHERITE GROUP

The crystal structure of the new mineral species owensite, (Ba,Pb)(6)( Cu,Fe,Ni)(25)S-27, is cubic, n 10.349(1) Angstrom, space group Pm3m. N ine S atoms bond to each (Ba,Pb) atom. The unit cell contains a single (Cu,Fe,Ni) atom that is octahedrally coordinated by S; the other twen ty-four (Cu,Fe,Ni) atoms are tetrahedrally coordinated. The structure is analogous to that of djerfisherite, K6Na(Fe,Ni,Cu)(24)S26Cl, but it contains no monovalent ions. The K sites in djerfisherite are here oc cupied by (Ba,Pb) atoms; the Na site is occupied by one of the (Cu,Fe, Ni) atoms, whereas the Cl site is occupied by a S atom. The structure was solved and refined to an R index of 5.2% for MoK alpha data to 28 = 100 degrees. The bond lengths and angles are all within the expected limits: Ba-S between 3.132(2) and 3.300(5) Angstrom, (Cu,Fe)-S betwee n 2.302(3) and 2.356(2) Angstrom [tetrahedral], or 2.501(5) Angstrom [ octahedral]. The Pb atom replaces the Ba atom within the S coordinatio n cage, but is disordered and displaced from the Ba atom position as a result of thr presence of the 6s(2) Pb electron pair. Four disordered Pb satellite positions exist, all 0.38 Angstrom from the Ba position, and in a square with a side of 0.31 Angstrom.