d="p-2">Green vesuvianite crystals occur with garnet and calcite in a hand specimen from the Nedvědice marble near Kozlov (near Štěpánov nad Svratkou, Svratka Crystalline Complex) in the Czech Republic. The average electron microprobe composition of the vesuvianite shows 12.10 wt% Fe2O3 (4.66 Fe pfu), 2.77 wt% B2O3 (2.45 B pfu), 1.71 wt% As2O5 (0.46 As pfu), and 1.40 wt% F (2.26 F pfu). The Fe concentration is the highest ever recorded for a vesuvianite-group mineral. The boron contents are extremely variable and two of the five compositions show more than the 2.50 B pfu needed for wiluite, and the average is only slightly less than this. The crystal structure [
d="p-3">Fluorine and OH occupy the O11 positions when there is a vacancy at the adjacent T1 position. Pentavalent As substitutes for Si at the Z2 site and Al at the Y2 site. The
d="p-4">The results showing Fe at three different sites with three different coordinations attests to the flexibility of the vesuvianite crystal structure. The incorporation of As at two different sites in the structure shows that rock-forming silicate minerals such as vesuvianite can be a reservoir for this heavy element.