Spectra recorded on the green spots of the section are characteristic of Cr3+ : two absorption bands are present in the visible range: one between 600 and 700 nm and one around 400 nm. The band in the NIR around 1050 nm is due to crystal field transition in Fe2+ ions. This iron band is mainly developed in colorless regions.
Above: Spectra recorded on the green spots with the first grating only.
Below: spectra recorded on a colorless crystal with both gratings.
