Copper percentage checking in Paraiba
Natural Tourmalines qualifying for Paraiba tourmaline colors are checked for copper and manganese by EDXRF machines. percentage of copper (cu) is checked and if requisite percentage is found it is graded as Paraiba tourmaline. If the tourmaline do not fulfill both the conditions it is not graded as Paraiba tourmaline.
in case the tourmaline do not qualify for Paraiba colors but has requisite amount of copper and manganese, it is graded as natural tourmaline and the copper comment is given so as to indicate that the stone is not Paraiba tourmaline but has copper and manganese in requisite quantity.