Abstract: Högbomite is reported from two upper-amphibolite and granulite-facies, sapphirine-bearing, Al-Mg-Fe-rich and silica-poor lens-shaped layers within the Bamble Sector, south Norway. Primary assemblages, indicating peak metamorphic conditions of 773–844°C at 7 kbar (Mg-Fe exchange thermometry),are spinel-sapphirine-biotite-gedrite, spinel-corundum-sapphirine-cordierite and orthopyroxene-biotite-cordierite-plagioclase. Högbomite formed by hydrous alteration and oxidation of primary spinel and rutile and/or ilmenite according to the generalised reaction: spinel + ilmenite/rutile ± sapphirine ± gedrite + H₂O + O₂ = högbomite ± corundum ± magnetite ± chlorite. Suggested conditions of högbomite formation are 550–620°C and 6–7 kbar. The högbomites contain 10.2–14.7 wt.% MgO, 0−.03 wt.% ZnO, 58.9–62.1 wt.% Al₂O₃ and 15.6–17.6 wt.% Fe as FeO. The two högbomites may belong to different polytypes, as suggested by their differing TiO₂ (9.9–10.1 versus 5.7–5.8 wt. %) and calculated Fe³⁺- and H₂O-contents. The partitioning of Zn between spinel and högbomite is not uniform and is considered to depend upon prevailing ƒ_o2 and α_H2O.