That is one funky tile…
To expand on a previous post, here is some more information about stone tile and grout cleaners.
Your stone floors starting to look a little grungier than you remember? It might be time for a good spring (summer, fall or winter too) cleaning. With stone tile surfaces, you want to make sure you are using the right type of cleaner. Many products are not designed for natural stone and can actually pose serious problems for your floor. Check out STONETECHPRO.COM for a selection of cleaners designed for your floors.
On a lighter note, if you live in the Dallas Forth Worth area and think you might just have the ickiest, dirtiest, nastiest grout around, check out the Moore Services website and you just might win a free tile and grout cleaning in their CONTEST.