How do I remove mineral stains from tiles?
i would suggest you try CLR.  It is available in most stores and hardware stores.  If this doesn't work, my question would be what type of tile do you have? Almost sounds like you may have an unglazed type of tile, not a highly glazed porcelain. If you are successful cleaning the tile, you may want to seal the tile to help in the future. You can find tile and grout sealers at any home center. 

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