a quartzite is a kind of metamorphic rock & sandstone is a kind of sedimentary rock ->  sandstone is a kind of sedimentary rock and quartzite is a kind of metamorphic rock  sandstone is a kind of sedimentary rock and quartzite is a kind of metamorphic rock & class is a property of a rock and includes values of sedimentary / metamorphic / igneous ->  sandstone is in the class of sedimentary rock and quartzite is in the class of metamorphic rock  sandstone is in the class of sedimentary rock and quartzite is in the class of metamorphic rock & a rock changes from sandstone into quartzite ->  the rock changes class from sedimentary rock to metamorphic rock  the rock changes class from sedimentary rock to metamorphic rock & as the class of a rock changes , the mass of the rock will stay the same -> the mass of the rock will remain the same