What are porphyroblasts and how do they form?
A Porphyroblast is a large crystal formed on the inside of Metamorphic rocks.metamorphic rocks (in)...crystals showing planar surfaces-namely, magnetite, garnet, epidote, mica, calcite, quartz, and feldspar. Minerals that have a tendency to form large single crystals (e.g., garnet) are termed porphyroblasts