I have a cute somewhat related story. I wanted to make really unique rings, so I decided to make them from some random metal from the forgotten realms of the periodic table.
I asked for a site that sells many rings of many different metals, with no luck. THIS metal, it turns out, is really difficult to cast. After many months with the idea shelved, one day my girlfriend found some chinese company that managed to do them. US$ 2k rings, and ugly as hell... but at least unique!
The girlfriend soon left me, but, well at least I still had the rings... until a few weeks ago when I noticed that I lost them too. C'est la vie :-)
When researching for this project, I did look up the densest metal possible: Osmium. Osmium has density of 22.59g/cm^3, which is 17% greater than gold's 19.28g/cm^3. (For comparison, lead is 11.34g/cm^3 and silver is 10.5g/cm^3.) Sadly Osmium melts at 5500ºF and can form toxic vapors, so making a ring out of it would be impractical.
Iridium has almost the same density as osmium (indistinguishable without precise instruments) and unlike osmium or rhenium it is neither toxic nor radioactive (even platinum is very slightly radioactive).
So iridium would be the safest among the densest metals for contact with human skin.
Unfortunately, not only iridium is very expensive, but it is extremely difficult to shape, being much harder and much less ductile than platinum (and its melting point is also much higher).
Platinum-iridium alloys are much easier to shape than pure iridium, but still much more difficult than pure platinum. In the second half of the 19th century, when new standard meters and kilograms were made for distribution in all countries and to replace the original standards made of pure platinum, an alloy of platinum with 10% iridium was chosen, as the most resistant metal to mechanical and chemical degradation that was known at that time but for which it was still possible to process it into a given size and shape.
I asked for a site that sells many rings of many different metals, with no luck. THIS metal, it turns out, is really difficult to cast. After many months with the idea shelved, one day my girlfriend found some chinese company that managed to do them. US$ 2k rings, and ugly as hell... but at least unique!
The girlfriend soon left me, but, well at least I still had the rings... until a few weeks ago when I noticed that I lost them too. C'est la vie :-)