| Popis: |
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. |
