Crystal chemistry of layered Pb oxychloride minerals with PbO-related structures: Part II. Crystal structure of vladkrivovichevite, [Pb^sub 32^O^sub 18^] [Pb^sub 4^Mn^sub 2^O]Cl^sub 14^(BO^sub 3^)^sub 8^-2H^sub 2^O

• Published in: The American mineralogist Vol. 98; no. 1; p. 256
• Main Authors: Siidra, Oleg I, Krivovichev, Sergey V, Turner, Rick W, Rumsey, Mike S, Spratt, John
• Format: Journal Article
• Language: English
• Published: Washington Walter de Gruyter GmbH 01.01.2013
• Subjects: Asymmetry; Chemical bonds; Crystal structure; Mineralogy; Minerals; Tetrahedra; Namibia
• ISSN: 0003-004X; 1945-3027

The crystal structure of vladkrivovichevite, a new complex lead oxychloride mineral from the Kombat Mine, Grootfontein, Namibia, has been solved by direct methods and refined to R1 = 0.048 for 3801 unique observed reflections. The mineral is orthorhombic, Pmmn, a = 12.759(1), b = 27.169(4), c = 11.515(1) A, and V = 3992.0(9) A3. The structure of vladkrivovichevite belongs to a novel type of layered Pb oxychloride structure. The structure contains 12 symmetrically independent Pb sites. All Pb sites have strongly asymmetric coordination. Two B atoms form slightly distorted BO3 triangles. One symmetrically independent Mn atom forms five Mn-O bonds and one Mn-Cl bond by forming MnO5Cl octahedra. The O1, O2, O10, O11, and O12 atoms are tetrahedrally coordinated by four Pb atoms each, forming OPb4 oxocentered tetrahedra. The O7 site has a remarkable octahedral coordination, consisting of four Pb and two Mn atoms. The O1Pb4, O2Pb4, O10Pb4, and O11Pb4 tetrahedra share common edges to produce bands interconnected by O12Pb4 tetrahedra, forming a ... layer. A O7Pb4Mn2 heterometallic oxocentered octahedron serves as the core of the ... clusters that link to the ... layer via BO3 triangles. The presence of ... clusters is associated with large cross-like vacancies in the ... layer. (ProQuest: ... denotes formulae/symbols omitted.)