Glow in the dark powder.   
This is strontium aluminate activated with europium.  It's a very good glow-in-the-dark material, of the type you expose to light to charge up.  It definitely works very nicely in that capacity, and can be charged in just a few minutes under fluorescent light.  I got a sample of three different colors on eBay: The seller offers larger quantities and different formulations besides what he sells on eBay. 
Not to be confused with our tritium glowing samples, which use the radioactive decay of tritium to glow for 10 or 20 years without any external input whatsoever. 
Source: eBay seller teddp 
Contributor: Theodore Gray 
Acquired: 5 September, 2002 
Price: $12 
Size: 1" 
Purity: <2% 
Sample Group: Powders
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