A calcite crystal demonstrating birefringence. The angle here is also showing a double image of the blue line. “Continue reading” for more details and photos. Crystals like this can have optical clarity and come from Iceland where they can weigh many tons. They are a stable polymorph of calcium carbonate (CaCO3).
To demonstrate phosphorescence (ie, persistence of fluorescence), I can simply turn off the light source or remove the specimen from the source. If it is rotated then there will be a streak of light apparent. Here is a drill for rotating the specimen.
A specimen lit up brightly with fluorescence.
As it rotates away from the light source the orange streak shows the phosphorescence. I could also show this in a high speed video. Well, how about that, my wife just bought one today. 
This specimen is opaque but fluoresces pink under long wave UV. 
The crystal form above with green fluorescence. Lit by a violet laser.
A calcite crystal under violet UV laser with double orange tracks of fluorescent birefringence.
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Photo Date: 2013, Jan , 2014