Indoor (kitchen), residential, tiles are 12" x 12", floors are 25 years old, nothing was sitting on the surface but it is near the frigerator/freezer, which leaks on occasion but not in that spot. Thank you!

Other important information that I should have mentioned: we are redoing the kitchen, plan was to replace everything except the floor. Everything is ordered, work is starting soon, and then this stain appears!

What is under the tile (concrete slab, or subloor over crawlspace/basement)?

You mentioned a leak, so maybe there is a bigger leak and the water is staining the stone from below? You don't want to proceed with your reno without knowing if you have to fix the floors first.

I think it's a concrete slab but I need to confirm that (it's an apartment building.) I'm wondering if that's the case... staining from below. I know that the problem with the freezer is that the drain gets blocked and it spills a bunch of water all at once--that I clean up quickly--and then stops. So I don't think there's a plumbing thing, but definitely will need to confirm that before we proceed. Is there a way to remove the stain?

Any updates?

Wet concrete slab and stone tiles equals a big wet splotch.

@SJ McCarthy Thanks for checking in...it is indeed concrete. The stain seems to be getting smaller, I guess it's drying out. Demolition has started and they haven't found any leaks--the foreman says he thinks the water is from condensation from the refrigerator.

@User Indeed! Can I assume that nothing needs fixing and it will dry out over time?

If the stain is already shrinking then yes it is possible it will dry out completely (ie. disappear).