Pure platinum has a Vickers hardness of only 52. Pt is alloyed with
other elements to increase the hardness for better wear resistance.
The most widely used of these is Pt90Ir10 with Hv 110, Pt95Ru5 with
Hv 135, and Pt95Co5 with Hv135. Some people cast Pt95Ir5 but the Hv
is only 80--a disaster for rings if you actually want to wear them.
TechForm Advanced Casting Technology