Raman spectroscopic study of spodumene (LiAlSi₂O₆) through the pressure-induced phase change from C2/c to P2₁/c

High-pressure Raman spectroscopy was used to follow the effects of a phase transition on the Raman spectrum of a natural specimen of the pyroxene spodumene, from its low-pressure (C2/c) to its high-pressure (P2₁/c) phases. The transition occurred at 3.2 GPa and was accompanied by an increase from 15 to 23 observed peaks, owing to a decrease in symmetry. Comparisons were made with other pyroxenes with the same space groups. The change in Raman shift with pressure of all peaks observed is reported. An additional change in the spectrum is observed between 7.7 and 8.9 GPa, possibly due to the formation of an additional bond between Li and O3 or some other transition that retained the mineral's P2₁/c space group. Splitting of the peak appearing at ∼700 cm^-1, used to characterize the P2₁/c phase in other studies, was not observed.