Labradorite

Last weekend, I came home with treasures from the annual fossil show I make a point of patronizing. Though they aren't properly accessioned by the Museum yet, the specimens I bought include a slab of amethyst crystal and a large Late Jurassic ammonite from Madagascar. Right before I left, the luminescence of a certain stone caught my eye--even more so when it was in my hand. The polished mineral, the size and shape of a bar of soap, is called labradorite, and the luminescent characteristic is called labradorescence.