A zincian högbomite and some other högbomites from the Strangways Range, Central Australia

Abstract

Zincian högbomite has formed by hydrous alteration of spinel and biotite in a lens of highly aluminomagnesian sapphirine-bearing granulite-facies rocks. The högbomite forms chestnut-brown {0001} flakes 1 mm across. ε = 1·827, ω = 1·852 (− 0·002). Analysis: BeO 0·10, SiO₂0·65, Al₂O₃ 59·69, TiO₂ 5·37, Ga₂O₃ 0·23, Nb₂O₅ 0·01, Fe₂O₃ 5·24, SnO₂ 0·06, NiO 0·04, ZrO₂ 0·03, MgO 7•69, Sc₂O₃ 0·01, CoO 0·11, ZnO 3·08, FeO 17·52, In₂O₃ 0·05, MnO 0·12. The pattern of d-spacings is anomalous. Other högbomites from the region have exsolved from cordierite or titaniferous opaque oxides.