Metamorphic rocks are formed when igneous, sedimentary, or other metamorphic rocks undergo a physical change due to extreme
heat and pressure. These chagnes often produce folded layers or banding in the rocks, and they can also cause pockets of
precious minerals to form. The folds and banding can be produced by incomplete segregation of minerals during recrystallization,
or they can be inherited from preexisting beds in sedimentary rocks or preexisting layers in igneous rocks. The precious minerals
can form as the result of recrystallization when the rocks undergoing metamorphism are subjected to changes in pressure and
temperature.