Acta Musei Moraviae

W-, Nb-, Ta-, and Fe-rich brookite from pegmatite near Bobrůvka, Strážek Moldanubicum (Bohemian Massif, Czech Republic)

Anatase, brookite, and rutile have been identified in small cavities along with albite, muscovite, tourmaline (Mg-rich schorl) and fluorapatite in pegmatitic material stored in the depositories of the Moravian Museum in Brno and originating from Houperk-hillock near Bobrůvka (Strážek Moldanubicum, Czech Republic). Primitive mineral compositions and simple structure of pegmatites show characteristics of anatectic pegmatites. Brookite shows a significantly complex zonation caused by variation in contents of W (up to 5.7 wt.% WO₃), Nb (up to 10.8 wt.% Nb₂O₅), Ta (up to 2.7 wt.% Ta₂O₅), Fe (up to 3.8 wt:% FeO) and Al (up to 0.5 wt.% Al₂O₃). X-ray elemental maps of the selected brookite crystal showed preferential incorporation into different structural levels corresponding to matching crystal faces via three different substitutions. Brookite from Bobrůvka represents the first occurrence of W-rich brookite worldwide. Mineral assemblage in pockets show transitional character from late pegmatitic to alpine-type fissures.