Single crystals of synthetic orthopyroxene were analyzed by Raman spectroscopy and electron microprobe in order to calibrate the effect of chemical composition on the position of Raman bands. For the Raman peak close to 670 cm−1 we obtain the correlations between Raman shift (RS) and chemical composition FeO(wt%) = −1.998 · RS(cm−1) + 1373.2 and MgO(wt%) = 1.4537 · RS(cm−1) − 959.02, allowing the determination of FeO with an accuracy of ±0.4 wt% and MgO with an accuracy of ±0.3 wt%, corresponding to less than 1 mole% ferrosilite or enstatite. A test of this calibration using natural orthopyroxene crystals shows larger deviations up to 3 wt%. These deviations can mainly be related to significant amounts of CaO and Al2O3, leading to an overestimation of FeO or MgO, respectively.

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