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 highpressure (P2 1 /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 P2 1 /c space group. Splitting of the peak appearing at ∼700 cm −1 , used to characterize the P2 1 /c phase in other studies, was not observed.
In situ Raman spectroscopy at high pressure was utilized to follow the phase transition of a synthetic sample of Li-aegerine pyroxene (LiFeSi 2 O 6 ) from its low-pressure (C2/c) phase to its high-pressure (P2 1 /c) phase. The phase change occurred between 0.7 and 1 GPa and was accompanied by a change in coordination of the Li atom from 4 to 5, which was confirmed by single-crystal X-ray diffraction. This is the first report of the Raman spectrum of Li-aegerine in the P2 1 /c phase. As was previously observed with other pyroxenes, additional changes in the Raman spectra were observed at pressures higher than the phase transition, including the splitting of the peak near 700 cm −1 , which has traditionally been utilized to indicate the phase transition. Comparisons with the Raman spectra of spodumene in both symmetries are utilized for a discussion of modes.
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