Chemical States of Colour-induced Cations in Colourful Tourmaline

X-ray photoelectron spectroscopy was used to investigate the chemical state and chemical environment of colour-induced metal cations in deep green,blue green,light green and pink tourmaline samples.The results show that both green and pink tourmaline samples contain Fe,Mn,Ti and Cr,but no Li and Be.Being Fe³⁺,Mn⁴⁺,Ti⁴⁺and Cr³⁺ respectively,the metal cations in different coloured tourmaline samples have the same chemical states. but they have different coordinated ions.Although varied Fe contents have been found in the green tourmaline samples,part of Fe coordinates with Fe occupying the Y position of the crystal structure。while no Fe has been found to coordinate with F in the pink tourmaline sample,all Fe in them occupying the Z position of the crystal structure,In the pink tourmaline sample Mn has been found to bond with Fe occupying the Y position,but in the green tourmaline sample most of the Mn bonds with 0 and only minor Mn coordinates with F.Fe and Mn in the tourmaline crystals are all in the state of Fe³⁺and Mn⁴⁺, and the charge transfer between the cation pairs is unlikely to take place.Thus the colour of tourmaline is probably induced due to the absorption of d-d ransition and charge transfer between oxygen and metal cations((O^2--M),especially due to the different chemical environment,such as coordination with different ions,impurity, and structure distortion.