Canadian agrellite fluorescence

Agrellite (NaCa_2(Si_4O_10)F) is found at a few localities around the world, notably the Kipawa river alkaline deposits in Québec in Canada. This sample, kindly supplied by Gérard Barmarin, comes from the Kipawa deposit. The spectrum is shown here excited by 254nm, 365nm (Hg lamp) and 404nm (laser) as purple, orange and redlines respectively. The dotted green line shows the white light transmission spectrum.

The image in the lower panel is a photograph of the sample illuminated by 254nm radiation and taken through an 8000 groove/inch transmission diffraction grating. The zeroth order image in the centre shows the fluorescence colour and the -1 and +1 orders to the left and right show the dispersed image. This shows clearly the bright near-UV fluorescence peak centred around 375nm and activated by trivalent cerium replacing some of the calcium in the crystal. The separated green-red complex (corresponding to the purple line spectrum above) is due to the lanthanide elements dysprosium and samarium together with some divalent manganese (see Emmermann, A. in "It's never 'Just and Activator'!" in the Journal of the Fluorescent Mineral Society, 2011).

Notes
1. The gaps in the spectra above are due to contamination by the residual mercury emission lines in the 254 and 365nm lamps.
2. The transmission grating used to make this image was the one I used to obtain the chromospheric and coronal eclipse spectra in 1999:
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