Porphyroblastic Texture

the uneven granular texture of a rock caused by the presence of large crystals, or porphyroblasts, in a fine-grained groundmass. Unlike phenocrysts, porphyroblasts form during recrystallization in the course of metasomatism of solid rock. Porphyroblasts include garnet, kyanite, staurolite, andalusite, microcline, albite, mica, tourmaline, topaz (in greisens), and aegirine (in fenites).