Figure 02. Sillimanite Porphyroblasts. White sillimanite porphyroblasts 2-3 cm in length, Rangely Fm., Walpole, NH, USA. The porphyroblasts are pseudomorphs after andalusite, demonstrated by remant chiastolite textures in some of the porphyroblasts. Although the regional metamorphic grade is in the andlusite zone, sillimanite has replaced the andalucite in response to a local temperature boost by the adjacent, syn-metamorphic Bellows Falls plution. John Brady photo.