Axel Emmermann (MKA/FMS)
Apr 19, 2018
This is the tip of a large kunzite crystal (130 * 30 *5 mm) in halogen light, 365 nm Convoy S2+, and MW-UV respectively. When lighted with halogen from below, through the base of the crystal along the c-axis, the color deepens dramatically, due to pleochromism. The violet color is caused by trivalent manganese, replacing aluminum. The orange fluorescence in the strong LW beam of the Convoy S2+ is due to manganese. There is also some chromium and some trivalent iron at play. The blue fluorescence in midwave UV is caused by oxygen defects (in the silicate groups) and very likely some [TiO6]8- groups (the same anion that causes the blue fluorescence of benitoite and dumortierite). The latter has not yet been fully investigated, however. There's a spectrum at http://fluo.mineralogie.be/