For his residency at the Thinking Tools research group, the German photographer Sascha Herrmann developed the project “Glimmer”. With this work Herrmann directs his glance towards the mineral world. The focus – in line with the medium of photography – lies on reflection and refraction. Herrmann’s series of C-prints is the result of spectral analysis, in which different stones have been illuminated by various light sources. A combination of microscopic techniques, photographic contact prints and short- and long-wave UV light makes visible the rocks’ refractive properties, such as opalescence and fluorescence for instance. Some of these properties are named after the rocks on which these properties were observed, and, conversely, some rocks are named after the particular light properties that these rocks exhibit. There is mica, a stone that gleams silvery, which in the Middle Ages has been sold as precious metal. Or the Iceland spar, that can polarize light—double it, that is—which is why it is used in several optical applications and also, of course, in photography. The artist decided to depict all the rocks – kyanite and opal, emerald and a moonstone – in front of a black backdrop. The resulting images therefore function as photograms, i.e. as negatives. The stones are put before an illuminated background and lightened from the front by a spotlight. This specific process of illumination is important because they divulge their features an properties only in light: they glow, they reflect and refract, they gleam and shine.