... 3(Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4Typical physical properties:Density2.82-3.32Hardness7 ... composite ceramic with the function of antibacterial sterilization and deodorization.Tourmaline have the special properties of piezoelectricity and pyroelectricity so it ... producing negative oxygen ion to antibacterial and deodorize.high pure tourmaline can be made into jewelry such as necklace bracelet and ...