Iridium

It is very hard and also it's brittle, which makes it very difficult to machine or work and, I guess, the latter limits the number of uses. Engineers don't like brittle materials.
HTH

According to my material database:
Platinum iridum alloy: Compressive strength 110-1285, elongation 1-40%, youngs modulus 180-285 GPa, vickers hardness is 90-410 HV, tensile strength is 245-1520 MPa.
I think it's too expensive and that you can get better materials for cheaper price in most applications.
Yep, I can see that it has good properties against everything. But why use a material that is better than necessary if the application doesn't require it and since the material is very expensive?
I don't see that iridium alloys should be brittle. You can also get it annealed. I have a reference: ASM Handbook, 9th ed. vol.2, p.693 for Platinum-5%iridium alloy, annealed: elongation is 20-40%
Med venlig hilsen / Best regards Martin Jørgensen

That would be a platinum alloy.

Oh yes, that's correct. I just searched for "iridium" in my database and the only thing that was found was 13 platinum iridium alloys (from 5-30% alloyed).
Perhaps platinum is always alloyed with iridium for practical purposes, anyone? I don't see any other materials together with iridium and I don't see the properties for pure iridium in my database...
Hard platinum-30%Iridium alloy, has 1-3% elongation, so this is brittle (and hard: Tensile strength is about 13-1400 MPa)... There is also an annealed version with properties for that in my database.
Med venlig hilsen / Best regards Martin Jørgensen