Melted gold is just as valuable as gold jewelry, since they melt it down anyway when you sell it. It might be worth marginally less than an intact piece of gold bullion that can be resold without processing.
Diamonds don't have resale value anyway. They're literally a scam.
Diamonds do have significant markup depending on where it is purchased but they do still have some value. As long as the buyer can verify the certificate and the diamond is of significant quality, size, clarity, etc. it still retains value. A gemstone buyer may offer less than a private buyer (just like with cars) because they are in the business of selling the diamond later for a profit. Obviously, there is artificial inflation from the manufacturers but everyone else still has to play in the inflated market.
As for gold jewelry, this can swing both ways. An intricate piece with some sort of history attached may fetch a higher price from a buyer that is interested in that versus a scrap buyer that will just melt it down.
Similar analogies can be found with cars. A factory stock 1996 VW Golf will only be worth slightly higher than scrap value. Meanwhile, a 1996 VW Golf Harlequin will be worth $8-9k, its the same car but with a different factory paintjob. Effectively no difference in manufacturing costs since it was just made from different stock-painted panels but worth way more to a buyer simply due to the history and rarity. The cars both still have the same scrap value, a junkyard would buy both of them for the same price.
One thing I've wondered, exactly how easy would it be to find a gold puddle after a fire anyway? I mean it's not going to vaporize or walk off on its own, but is it just going to be a little solidified glob there to pick up or what?
Yes, it might flow around in the fire but it would be in the same area. A metal detector would be the fastest way to find it. Likely less time to find it solidified than looking for jewelry on a beach. Certainly less time than mining the gold.
I've found aluminum globs under fires that had cans or trashed roofing thrown in. Pretty clean, since nearly everything floats on it, and easy to spot in ashes.
Once the core of the fire is mostly charcoal temperatures can climb up to 1100C. It doesn't have to be windy or even a large fire. Just need to be burning charcoal and not evaporating water or burning off volatiles.
The fires I have found aluminum globs in were long burning beach campfires and a bonfire to burn brush(big fire). The beach campfires were moderately sized but they certainly weren't bonfires built with 6-8 foot logs.
