Rust stain on terrazzo floor

Try making a poultice (paste of Barkeepers Friend powdered cleanser and water), apply to the rust area, cover with some plastic wrap and tape down the edges with freezer/blue painters tape. Leave overnight. Next day, gently wipe it up, rubbing a bit as you go. I’ve used this method to get rust out of my white marble countertops, and terrazzo is made of marble chips set in concrete, isn’t it?