I would have thought mineral build-up, as well, but that is strange it is only on the perimeter. Could it be coming from the walls? A co-worker of mine covered a stain in her grout with a colored grout sealer. You could check with a flooring company or home depot/lowes like store to see if they have a colored sealer that would match your grout. She said the best way to apply grout sealer is with one of those plastic mustard or ketchup containers because the pointed lid is the perfect size for grout.

I have used colored grout sealer from Home Depot and it works great. This was used on DDs awful, old, kitchen counter grout. The previous owners never cleaned. I used a child's waterpaint set paint brush to paint it on, and wiped with a vigorous rub using paper towel every now and then to remove overage.

Never thought to just cover it up. Good idea. Still wonder what the heck it is. It's like cement! Thanks,guys!

Sounds like mineral deposit. I was able to remove the mineral deposit around my faucets on my black granite by soaking a paper towel strip with straight vinegar. Let it sit a couple of hours and kept it wet with vinegar and easily scrubbed it off with a toothbrush. Would Lime-Away work???

I would suggest posting at the John Bridge tile forum - great hangout for professionals and DIY'ers and the experts are generous w their advice. If new tile, it may be "grout haze" - go to www.johnbridge.com and then to the tile cleaning forum.

Good luck,

L