Discrete nodules (0.5-1 cm in diameter) of rutile, containing 6.5-20.9 wt.% Nb2O5, 5.2-8.2 wt.% Cr2O3 and 0.76-1.35 wt.% Zr, occur in the Orapa kimberlite in Botswana. The data expand the compositional range of rutile from the upper mantle and provide the first direct evidence for metasomatism at this locality. Coarse (1-2 mm) lamellae of Mg-Cr-ilmenite are intergrown in the Nb-Cr-rutile. The equilibrated intergrowths of rutile and ilmenite are possibly related to high-P crystallographic-shear structures of the alpha -PbO2 type.-L.T.T.
