As seen on Game of Thrones the TV series, some gold is melted in a regular campfire.
Is this physically and chemically possible?
Gold melts at 1064 °C, however, in jewellery, gold is often alloyed with copper (wiki). Though copper melts at 1084 °C, the alloy has a lower melting point, as you can see from the phase diagram (note that the temperature is in Kelvin, which adds ~271):
If the crown is 18k gold (¾ gold, ¼ copper), which makes an alloy that is harder than gold or copper alone, and gives a nice reddish hue to the gold, then the campfire only needs to be able to produce ~900 °C, which is achievable with the right fuel according to @ratchet freak's research.