how do you remove rust from travertine?

Answer 1

Travertine is a very porous stone. It absorbs stains very easily. If it wasn't sealed, more than likely, it isn't coming out. Perhaps a diluted acid wash, or some cleaning solution specifically for rust. Try asking a tile contractor (which I am, and I don't know) or a local tile wholesaler. If you try to clean it with the solutions, try it in a hidden spot, if you have one, to see if it works without making things worse. But knowing the nature of the stone, you are probably stuck, unless you replace the piece(s)
Sorry.

Answer 2

You can try a cleaner like CLR which is to remove rust - but try it on a very small area - you can also clean stone and brick with a Muriatic acid solution but be careful mixing and using it.