Figure 6.22o. Monazite Core and Rim Ages. Monazite grains in some rocks have prominent chemical and age zonation. These images of a monazite grain from a cordierite-replaced garnet include chemical maps of Pb, Y, and Th, backscattered electron, and thin section images. The monazite rim ages record growth of monzazite during the nearly isobaric cordierite producing reactions. Data from Cheney et al. (2004). J.T. Cheney photos.