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Two types of V-rich dravitic tourmaline (oxy-dravite to dravite) distinct in their color, morphology, paragenesis and composition from graphite quartzite at Bítovánky near Trebíc, Moldanubicum, Bohemian Massif, were studied by means of electron microprobe and single-crystal X-ray diffraction. Green oxy-dravite (GVD) from graphite quartzite is sporadically zoned with V-enriched rims; brown oxy-dravite to dravite (BVD) from mobilized quartz-rich nests is characterized by such V-enriched rims. The formulae derived from chemical and structure data of the two oxy-dravite varieties are X(Na0.534Ca0.284 0.164K0.018) Y(Mg1.461V0.679Al0.771Fe0.042Mn0.003Ti0.043) Z(Al5.074V0.237Mg0.689) T(Si5.782Al0.218O18) (BO3)3 [(OH)3.058O0.75F0.192] for GVD and X(Na0.539Ca0.148 0.297K0.017) Y(Mg0.992V0.302Al1.039Fe0.582Mn0.011Ti0.068Cr0.007) Z(Al5.339V0.082Mg0.578) T(Si5.864Al0.136O18) (BO3)3 [(OH)3.209O0.621F0.171] for BVD, respectively. Both types of V-rich oxy-dravite feature Al-Mg-V disorder between the Y and Z sites; V and Cr are preferentially located at the Y site. The V-rich oxy-dravite from Bítovánky has unusually high Ca contents and high proportion of vacancy at the X site. High concentrations of V in the GVD and late BVD probably result from hydrothermal dissolution of (Ti,V)-oxides during a high-grade metamorphic overprinting of the host graphite quartzite assemblage

Crystal structure and compositional evolution of vanadium-rich oxy dravite from graphite quartzite at Bítovánky, Czech Republic