Black stains did not come out when sanded

Q: I just had older Oak floors refinished. They are approximately 40 years old. There were black stains in the hall way that would not come out when sanded. We kept the floor stain the same as the original but the black stains look horrible.

Would you suggest restaining the floors a darker color so the darker stains won’t show as much? We are in the process of fixing up this house to sell.

A: Your floors are probably 3/8″ thick, top to bottom and are good for 2, maybe 3 sandings. I think I would get your real estate agents opinion about colour. But keep in mind, this floor is thin to begin with. You either leave it as is, or remove/replace the stained areas and start over.