  Cadmium shielding foil. 
This is fairly thin cadmium foil said to come from a nuclear research facility and intended for use as radiation shielding.  Lead is much more common as a shielding material, but cadmium works better for neutrons, which tells you this came from a serious place, as neutrons are not something you get from common radioactive minerals and the like. 
Source: Anonymous 
Contributor: Anonymous 
Acquired: 24 December, 2007 
Text Updated: 8 March, 2008 
Price: Donated 
Size: 5" 
Purity: 99%
 |  
  |  
 |  
  |