Here's the volcanic rock claim too.
http://www.talkorigins.org/faqs/faq-.../age.html#k-ar

Scroll up for a couple of more general statements on radiometric dating.

And yes, everything I've heard about C-14 is that it's only useful for non-living tissues, because living tissue continually collects C-14, and it only starts decaying once the biological processes have stopped. So that shellfish is right out.

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...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere