Many metamorphic rocks contain large and beautiful crystals.
The diverse colors and textures of these rocks resulted from different combinations of temperature and pressure produced by interactions of the gigantic plates that cover Earth's surface. Svea Lin Rodgers, Smithsonian National Museum of Natural History. Presented by the Indiana Academy Office of Outreach Programs , the UPS Foundation , the National Museum of Natural History , the Natural Partners Program , Ball State University , and Ball State Teachers College .