Quartzite, also a natural metamorphic rock, is created through centuries of pressure and heat on sandstone, which causes its structural crystals to fuse into a new rock that is incredibly hard and beautiful resembling marble. Quartzite’s natural colors are lighter, often in shades of gray, like marble, but certain natural minerals can also give a more colorful tone. Though less porous than marble, raw quartzite is too porous to make it practical for use such as kitchen counters. To make quartzite usable and less prone to scratching, staining or etching, the fabrication process includes a coating of sealant of polyurethane, wax or acrylic. To maintain a nonporous finish, quartzite must be resealed now and then.