Acta Musei Moraviae

Nordenskiöldine CaSnB₂O₆ from the locality Kozlov near Nedvědice, new rare accessoric mineral for Nedvědice marbles

Very rare mineral of Europe – nordenskiöldine CaSnB₂O₆ – was found in Sn-rich calc-silicate assemblage (tin skarn) of Nedvědice marbles near Kozlov (4 km N from Nedvědice, western Moravia). It forms rare euhedral grains approx. 3–10 μm in size enclosed in calcite. Nordenskiöldine was identified using an electron microprobe, its chemical composition (Ca_{0.965–1.020} Mg_{0.003–0.007} Fe_0.005 Mn_0–0.003) Sn_{0.990–1.013} (B₂ F_0–0.039) O₆ corresponds to the theoretical formula. Besides calcite the mineral assemblage contains vesuvianite, Sn-andradite, malayaite, fluorapatite, cassiterite and stokesite. Nordenskiöldine crystallized as primary Sn-B skarn mineral under conditions enriched especially in B₂O₃ and poor in SiO₂ and CO₂.