Here is a picture of some uranium (vaseline, carnival) glass marbles that are arranged in a Christmas tree pattern. The top marble is an orange-reddish fluorescent under ultraviolet (UV) light. The fluorescent activator could be magnesium. The trunk marble is just a brown swirled glass and has no fluorescent properties.
The tree glows when exposed to black light from a compact fluorescent bulb. See one here: http://www.ebay.com/itm/Ultraviolet-UV-LW-Black-Light-Bulb-Fluorescent-calcite-mineral-uranium-marbles-/110785264269?pt=LH_DefaultDomain_0&hash=item19cb50fa8d#ht_981wt_1365
See the Christmas tree pattern marbles here: http://www.ebay.com/itm/Christmas-Tree-Pattern-5-UV-Light-Fluorescent-Uranium-Vaseline-Glass-Marbles-/110785256231?pt=Marbles&hash=item19cb50db27#ht_663wt_1365
