The morphology of bronzite phenocrysts (Ca5Mg75Fe20) in the chilled margins of a diabase dike in eastern Connecticut indicates that this mineral crystallized with a monoclinic form and later inverted to orthorhombic pyroxene. Oscillatory zoning, sector zoning, and very faint basal exsolution lamellae in the bronzite of the coarser-grained parts of this dike also reveal the previous 2/m symmetry of this pyroxene. The (100) lamellae, so typical of bronzites, are preferentially developed in the (100) and (100) sectors of the Connecticut bronzite. Their development may be related to the monoclinic → orthorhombic inversion. Crystallization of clinobronzite in this diabase suggests that bronzite in many other igneous bodies may have crystallized with monoclinic form.