摘要
Tourmalines from various deposits have been studied by UV-Vis and X-ray spectroscopy.As a cyclosilicates mineral,tourmaline has a very complex chemical composition with various colors.The general formula is XY3Z6 (BO3)3Si6Ols (W)3V.The crystal field theory was used to examine for confirming tourmaline color.Mn-rich tourmalines from Zambia showed yellow color.It was attributed to the Mn2 +-Ti4+ IVCT (intervalence charge transfer) and O- hole trap center.Mn2 +-Ti4 + IVCT showed the absorption band at 320 nm and 0-hole trap center had the absorption band at 365 nm.Brown tourmaline from Madagascar contained a lot of Fe and Mn.Mn2+ ion was responsible for light pink color due to the d5 configuration.But the dark pink tourmaline was colored by Mn3 + ions because the d4 configuration of the Mn3 + had the spin-allowed ' d-d' transition.Its absorption band occurred at 530 nm.The green color resulted from Fe2+ ion due to splitting of 3d6 'd-d' transition.On the other hand,Cu2+ ion was responsible for the blue,which had the 3d9 configurations and showed the absorption bands in the neighborhood of 700nm and 900 nm.Therefore,Cu-bearing tourmaline (Paraiba-type) from Mozambique showed greenish blue or bluish green.