The term "bluestone" came out of the paving industry to identify a type of sandstone that contains quartz particles. Typically excavated from quarries in the Northeast United States, the blue-toned sandstone continues to maintain popularity with homeowners as a paving and masonry material. The absorbency of unsealed bluestone, however, makes it susceptible to staining, including rust stains caused by metal objects left in contact with the stones for long periods of time. Remove stains with a non-toxic poultice, which will leach the rust from the pores of the stones.
Clean the stained areas, scrubbing with hot water and dish soap. Rinse the washed areas with clean water.
Purchase a dry, absorbent, powdery material for the poultice. Options include kaolin clay powder, diatomaceous earth, whiting chalk, molding plaster or talc.
Place enough dry material in a mixing container to cover the rust stains. Use approximately 1/2 lb. of dry material for every 6 square inches of staining.
Add organic, acid-free rust remover to the dry material. Combine and mix the rust remover into the dry material gradually, until a paste-like consistency is reached.
Dampen the stains using a spray bottle. Apply the poultice while the stained areas are still wet. Spread semi-thick layers of poultice over the stains.
Place pieces of plastic wrap over the poultice-covered areas, taping around the edges with packaging tape. Allow the poultice to leech the rust stains overnight or until the poultice has fully dried.
Remove the pieces of plastic wrap and rinse the dried poultice. Apply a second treatment of poultice, if any evidence of the rust remains.