You don't even need a super high temperature to burn a ruby. If you poured lava on them, they'd be fine. However,if you poured ACID on them, it would probably scorch their skin, or at least cause pain. Same thing probably applies to bismuths. We know they can resist extreme heat, but there's nothing that suggests they can resist CHEMICAL burns.
that’s why the deadliest tree in the world was on the list I made that one time of things on earth that can kill gems