can diamonds be harmed by fire?

Depends on how long the diamond was exposed to high temp and to what temperature it was heated.

Diamond is a metastable form of carbon, so heating it can case the diamond bonds to re-organize themselves into graphite bonds.

However - we are talking about gething the diamond up to well about 1000Kelvin - so it's unlikely to be a problem

I imagine that the gold would deform or melt at those temperatures.

If it happened - restoration isn't a possibility

true diamonds cannot be harmed by fire. The gold may have been partially melted and deformed, but the stone(if it was a real diamond) should not have been affected, no matter how long it was in the fire pit. If the setting(ring) is unaffected a toothbrush with some toothpaste should take any smoke off, afterwards you may want to take it to a jeweler and have them put it in the ultrasonic wash for about 5 minutes to make it sparkle again.

You can't make a fire that will harm a diamond. Throw it into the sun during your next orbit and maybe you're talking some damage. The gold on the other hand.....bty why do we put the hardest substance known to us in one of the most malleable?

The gold will probably need professional restoration. At least it won't need cleaning for a while...

Thies diamonds can be destroyed by fire or damaged by fire depending on the severity of the heat and how fast it is cooled I would take it to a restoration company or a well-known jeweler

I don't claim to be an authority, but given the extraordinary temperatures required to form diamond, I doubt that any normal fire would harm it. I would imagine that it could get dirty though, so youmay want to bring it to a jeweler to have it cleaned (and maybe inspected if you're concerned).

The diamonds shouldn't be harmed by the fire, at all. They will not look as 'polished' as they did when you bought them, so a clean may be in order..