[kens]

I was puzzled by this, since obviously there are elements that are more rare than iridium, so I checked the original data source. They eliminate most radioactive elements which kind of makes sense. I was a bit surprised to learn that polonium and radium are less common in the crust than iridium. They also eliminate noble gases from the list, of which krypton, xenon, and radon turn out to be rarer in the crust than iridium. Also a couple sources have rhenium rarer than iridium.

(I'm not trying to be pedantic and start an argument, but just fill in some information in case anyone else wondered about this data.)

See http://en.wikipedia.org/wiki/Abundances_of_the_elements_(dat... and http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earths...