Hi Adam, we have seen this many times. Especially in some limestone showers. Try wiping it down with some bleach. Rinse the surface after a few minutes. It should disappear. Most of the time this has worked for us. We learned this a few years ago

When one of my guys let water sit too long on a limestone floor. Next day the entire surface was brown. We did the bleach trick and very quickly the floor was back to its normal Color.

BlackStone Marble Care

Sent from my iPad

On Apr 5, 2016, at 7:38 PM, Adam Bartos <info@restoreyourtiles.com> wrote:

Last week we cleaned limestone walls and floors for the residential customer using our truck mount. We came back yesterday to seal the floor and were surprised by the look of one slab, with one continues stain at the bottom. It lookes like iron oxidation and it is only 1 slab out of 6. We tried iron out but that didn't help.
Any idea why something like that happened?
What can I use or do to remove it?
I am going back there on Thursday and I need your help very badly. I am puzzled and without any ideas. I am attaching picture for u to see it.
Thanks
Adam Bartos
BiO Tile

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