This is how the specimen shown in photo DPS17a appears under a longwave ultraviolet LED light source. The red fluorescence almost certainly is due to manganese as the Mn2+ ion substituting for Mg2+ in the diopside structure. The diopside was confirmed as such both by Raman spectroscopy and X-ray fluorescence analysis. The chemical data also confirmed its low iron content (only 0.54 wt.% FeO), consistent with its abnormally pale color. Discussion of this specimen, plus fluorescence emission and excitation spectra of the diopside, were presented in Verbeek et al. (2018). Since publication of that paper, several additional specimens of red-fluorescing diopside from the Franklin orebody have been discovered, all of pale tan to nearly white color.
Identifier: DPS17b Locality: Franklin mine, Franklin Specimen size: 9 x 5.5 x 4 cm Photo credit: Earl R. Verbeek
