Scarodactyl posted:

Heat resistance varies quite a bit from stone to stone. Sapphires are fine up to around 2000c (though these temperatures can certainly affect them, hence heat treatment), but beryl (which emerald is a variety of) will turn to opaque white ash around...I think 800ish c? I've done it once, it wasn't pretty.
For a specimen like this, though, you're not dealing with a single crystal, but a specimen composed of many intergrown crystals of different minerals. They will have different heat tolerances and different rates of thermal expansion. They're also much harder to clean, impossible in many cases to get soot out of fine crennelations, vs a single crystal or faceted stone.

So yeah, a fire could totally destroy a specimen like that with ease. That said, their valuation is insane even by massively-inflated-valuation standards, and I think it's fair to disbelieve anything they say.