Eka-Thorium
Now, this is neat: A superheavy element (Z=122, A=292, tentatively named "eka-Thorium" or "unbibium") which is relatively stable (t_1/2 ≥ 10⁸ yr) has been observed in nature, in natural Thorium samples. (It's called eka-Thorium because it would sit directly below Thorium on the periodic table; as a result, it's chemically very similar to Thorium, which means it can mix in to Thorium ores and stick there because it doesn't separate very easily)

This is a whole 30 atomic numbers above the next-largest naturally occurring element, Uranium. (Z=92, A=238) It's the first empirical proof that superheavy nuclei can actually exist and be stable.

Edit: Some history - the last time an element was discovered in nature was Francium (Z=87), which was discovered in 1939 by Marguerite Perey. It was thought highly likely that that would be the last time anyone ever did.

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