How To Clean Rust Off Limestone?

Limestone does not rust, but the metal fixtures attached to limestone do rust and in our case - this is what happened.  NOw the limestone is stained.  This is a valid question.  Our home is over 100 years old, so I am interested in learning about a process that will remove the run without damaging the stone.  Any one?  Thank you.

Poultice with Oxalic acid + powder + water. This poultice will etch polished marble, limestone and travertine and repolishing will be necessary.

I'd try vinegar first...a light acid...if that doesn't work use a rust remover for laundry and scrub brush...if you're not too worried about the stone, then just go get some muriatic acid, masonry section of hardware store