I have soldered tips on gold prongs with very hard solder with no
problem as long as the diamonds were heavily coated with boric acid
and alcohol. As long as they are squeaky clean and well coated there
should be no problem unless they are treated or filled.
We have used plat solder next to diamonds but only the very lowest
like say 1000 or 1100C. It gets pretty dicey at that temp and the low
temp plat solder is not a great color match.
So if I had to pick a number I’d say around 1100 C or higher will
smoke them. When that happens they go to the diamond cutter to be re
Have fun and make lots of jewelry.