The parent rock for marble is limestone.As temperature and pressure increase on a body of limestone underground, calcite crystals begin to fuse together and recrystallize.   Pure limestone is white, but marble can be any color based on the impurities that may have existed in the original limestone rock.   Marble is an excellent building stone due to its uniform texture, softness (calcite is a 3.5 on Mohs hardness scale), and inherent beauty