Six natural tourmaline crystals with different colors were investigated by near-infrared
(NIR) absorption spectroscopy. The tourmaline crystals were obtained from Lucyen mines in
Vietnam. The NIR absorption spectra were recorded in two ranges of 4000-5000 cm-1
and 6500-
8000 cm-1
. We found, according to their NIR spectra features, these six tourmaline crystals can be
classified into four groups: G1, liddicoatite; G2, elbaite; G3, dravite; and G4, Uvite. This grouping
is consistent with the chemical composition analyses and our earlier Raman studies.
