In article ,
Andy Hall writes:

That's more cosmetic, AIUI. The "gold" caps (I have some as well)
are gold and platinum or other noble metals. I'm told that they are

IIRC, my dentist told me they are a gold and copper alloy, pure
gold being unsuitable. NHS ones are apparently much more copper,
and not worth recovering the gold from.

I did have a rear gold crown 20 years ago. When it failed, my
dentist built the tooth back up with the white quartz resin,
onto which another gold crown was going to be fitted. However,
I wanted him to try leaving the white quartz resin, which has
now lasted some ~15 years in that position. He always comments
on how unorthodox that fix is, and how he's surprised it's
lasted so long. A tiny bit did chip off recently, so it may be
coming to the end of its life, but I'll have the same thing
done again when necessary.

--
Andrew Gabriel