The Ironwood Spell says both that "While remaining natural wood in almost every way, ironwood is as strong, heavy, and resistant to fire as steel." and that "...ironwood does not burn. "
So if it doesn't burn... If you brought it to a heat that would cause steel to melt, would the ironwood melt as well?
Would it vaporize?
Would it just be non-specifically 'destroyed'?
JET FUEL CAN'T IGNITE IRONWOOD!
I imagine it would crumble.