The fluorescence of ruby, sapphire and emerald
The photo-luminescence of natural crystals of ruby, sapphire and emerald (beryl) has been studied at room temperature with a Fuess spectrograph of high light-gathering power. The ruby has yielded a number of new bands which have not been obtained hitherto. The spectrum of sapphire corresponds closely to that of ruby but with slight differences. The spectrum of emerald consists of two sharp lines at 6806 and 6835 accompanied by other diffuse bands and is compared with that of ruby. The fluorescence in sapphire and emerald is also discussed with respect to the origin of luminescence in them. Photographs of the spectra illustrate the paper.