I know little bit about astrology relating to gems.
Hessonite garnet (gomed) is mostly worn on silver metal but it can also be worn in gold when prescribed by astrologist. I wouldn’t say that wearing a hessonite garnet in gold would bring adverse effect but to get the best result of hessonite it should always be studded in silver metal.
I don’t know if it is true that hessonite should not be worn with yellow sapphire. But, if it is true then hessonite should also not be worn with yellow topaz and citirine.
Though I’m positive that hessonite should not be worn along with ruby, coral and pearl or combination of these stones.
In case if you don’t know, here is a link which explains the benefits of wearing hessonite garnet http://www.gemstonebuzz.com/meaning/hessonite and properties of hessonite garnet http://www.gemstonebuzz.com/grossular.
🙂