Thanks, peoples. Y'all know your floors. All comments (and links)
read and duly noted.
-Yea, it's possible it could have been dog urine that caused it. The
stain wasn't noticed for quite a while though because, at the time,
there was a carpet covering it.
-The stain actually is in a very prominent place in the living room.
My take on the comments here is that refinishing the whole floor will
result in the best final appearance. Incidentally, the stain is
circular, about 5in diameter. The room is about 400sft (actually, the
floor covers the living room and the dining room. The two rooms are
conjoined, with only an archway between them (no door separating the
-I don't really know how deep the stain is. Too deep and I see the
advise that I'll have to replace the boards AND refinish the whole
floor. I'm supposing that's because there's a limit on how much you
can sand away the floor before you're compromising it's integrity too
-By the way, there are no closets in the room, so no available donor
pieces for a graft.
-Oren asked me to post a pic. But, as far as I know, you can't post
pics here. At least I don't recall ever seeing any pics on Usenet/