How to oxidize tantalum? I am interested in learning how to oxidize tantalum. I have seen some tantalum rings that the sellers say is a permanent smokey blackish color. But I've spoken to some people that say tantalum cannot be oxidized, and the rings I saw must have been coated.

So anyone know if and how tantalum can be oxidized?
The smoky black stuff is probably not tantalum oxide.  The only such oxide that's well characterized is $\ce{Ta2O5}$, which is white.  Tantalum itself is a rare element, so if the jewelry contains tantalum at all it's probably a thin coating or cladding on a base metal substrate.