Original paper

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

Koshlyakova, Natalia N.; Zubkova, Natalia V.; Pekov, Igor V.; Giester, Gerald; Pushcharovsky, Dmitry Yu.; Chukanov, Nikita V.; Voudouris, Panagiotis; Magganas, Andreas; Katerinopoulos, Athanassios

Abstract

Anthropogenic vanadates with garnet structure were found in old metallurgical slags from the Lavrion mining dis- trict 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)O 12(mineral name schäferite), {NaCa2}[Ni 2](V5+ 3)O12 and {Na 3}[Fe 3+ 2](V 5+ 3)O12. The main scheme of heterovalent isomorphous substitutions is: Na++Fe3+ ↔ Ca 2+ + M 2+, with M 2+ = Mg, Ni. The crystal structures of two crystals with different Mg:Ni ratio, {Na1.5Ca1.5}Σ3[Mg 1.1Fe3+ 0.5Ni0.4] Σ2(V2.8P0.2) Σ3O12(1) and {Ca 1.7Na1.3}Σ3[Ni 1.0Mg0.7Fe 3+ 0.3] Σ2(V2.8P0.2) 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).

Keywords

lavrionmetallurgical slagvanadate garnetgarnet groupcrystal structureschäferite