  Autunite.  
This autunite was donated by the mine owner who dug it up: It's a lovely specimen, photographed here under ultraviolet light.  You can get samples of this an other radioactive minerals direct from the mine. 
Source: eBay seller boomologist 
Contributor: Theodore Gray 
Acquired: 25 June, 2005 
Price: Donated 
Size: 1.5" 
Composition: Ca(UO2)2(PO4)2.10H2O
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