GEOLOGY

Detailed explanation-1: -Common metamorphic rocks that may host gem minerals include schist, gneiss and marble. The type of gem mineral occurring in metamorphic rocks depends on the conditions of metamorphism and the composition of the original rock prior to metamorphism.

Detailed explanation-2: -Large amounts of granitic intrusions are also associated with regional metamorphic rocks. The most common regional metamorphic rocks are slates, schists and gneisses.

Detailed explanation-3: -The rock cycle shows that both igneous and sedimentary rocks can become metamorphic rocks. And metamorphic rocks themselves can be re-metamorphosed. Because metamorphism is caused by plate tectonic motion, metamorphic rock provides geologists with a history book of how past tectonic processes shaped our planet.

Detailed explanation-4: -Gneiss, the highest grade metamorphic rock, contains bands of easily visible quartz, feldspar, and/or mica.