The crystal structure of the compound Pb6Cu+(AsO3)2Cl7 discovered in the ancient slags of Lavrion, Greece

Lead and copper(I) chloride arsenite was found in the ancient metallurgic slag from the Vrissaki area, Lavrion district, Attikí Peninsula, Greece. Its chemical composition corresponds to the idealized formula Pb6Cu+(AsO3)2Cl7. The IR spectrum shows the presence of AsO33- anions and only a trace amount of O-H bonds. The crystal structure was solved by direct methods and refined to R(F) = 0.0304 based on 1778 unique reflections with I > 2s(I). The compound is trigonal (rhombohedral), R3, a = 9.8691(2), c = 34.2028(13) Å, V = 2885.01(14) Å3, Z = 6. Two crystallographically nonequivalent As3+ cations occupy apexes of the AsO3 pyramids. Cu+ cation occupies an apex of the CuCl3 pyramid. The group [Cl3Cu-AsO3] is arranged along the c axis. Pb cations occupy two sites with seven- and eight-fold coordination. The crystalchemical formula of the compound is Pb6(Cu+Cl3)(As3+O3)2Cl4

Crystal chemistry of vanadate garnets from old metallurgical slags of Lavrion, Greece

Anthropogenic vanadates with garnet structure were found in old metallurgical slags from the Lavrion mining district in Greece. They occur as brownish to blackish isometric crystals up to 2 mm across and are associated with anthropogenic counterparts of liebenbergite, trevorite, bannermanite, albite, nosean, haüyne, etc. The studied vanadate garnets form a ternary solid-solution system with the end-members {NaCa2}[Mg2](V5+3)O12 (mineral name schäferite), {NaCa2}[Ni2](V5+3)O12 and {Na3}[Fe3+2](V5+3)O12. The main scheme of heterovalent isomorphous substitutions is: Na++Fe3+ → Ca2++M2+, with M2+= Mg, Ni. The crystal structures of two crystals with different Mg:Ni ratio, {Na15Ca15}Σ3[Mg11Fe3+05Ni04]Σ2(V28P02)Σ3O12 (1) and {Ca17Na13}Σ3[Ni10Mg07Fe3+03]Σ2(V28P02)Σ3O12 (2), were studied. Both are cubic, space group Ia-3d, with a = 12.388(3) Å (1) and 12.387(3) Å (2), V = 1901.1(14) Å3 (1) and 1900.6(14) Å3 (2) and Z = 8. Final R values are 0.0245 for (1) and 0.0237 for (2). © 2016 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany