Fig. 1.

Measured and calculated absorption spectra of an olivine with Mg/(Mg + Fe) = 0.89 at different temperatures. The symbols are data measured on a 3.6 mm thick olivine plate while the solid lines are spectra measured with a 0.8 mm thick plate. The dotted lines indicate spectra measured on submicron-sized olivine grains embedded into PE pellets. The dashed line represents the calculated room-temperature absorption coefficient based on optical constants by Fabian et al. (2001), the dash-dotted line that for forsterite at 50 K after Suto et al. (2006), both for the average of the crystallographic orientations.