  Poster sample.
This mineral, Torbernite, appears in my Photographic Periodic Table Poster representing protactinium, because this highly unstable element can't reasonably be photographed. The rock probably contains on the order of a few atoms of protactinium at any one time, as part of the complex decay chain of the uranium that makes up a much larger fraction of the sample. In no meaningful way is protactinium itself visible in the sample, but sadly that's about the best you can do with an element like this. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.
Source: eBay seller migalf1
Contributor: Jim Markitell
Acquired: 3 June, 2005
Text Updated: 4 May, 2007
Price: $27
Size: 1.5"
Purity: 0%
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