I put a real stone (all rough surfaced) tile floor in my entry hallway, kitchen, downstairs bathroom and hallway about eight years ago. Not knowing much about tiles I used a variety of foot square tiles of different stone types and colors with very thin grout lines. Altho I used a high quality seal at installation, over the years the tiles darkened considerably with accumulated dirt.
I called Ben at Turbo Clean to ask him whether he could get the tiles looking really clean. He said he couldn't make any promises but that with his heavy duty equipment the chances were good he could.
He came over and spent about 3.5 hours on 550 square feet of tile. His heavy duty pick-up pulled a monster industrial trailer that he said could put out very high pressure and he said he would use an enzymatic cleaner.
When he finished the tiles, including the white stone tiles, were about 99% as bright and colorful as when I first installed them. I was amazed to see the snow white squares go from brown back to white. The price was $260 which included $40 for a new wax seal. I was very impressed and think I will get this done every couple of years in the future.
The only downside is that his industrial trailer, which he parked outside my front door makes quite a noise part of the time and it took an hour or two for the wax vapors to dissipate. So, if you want waxing as part of the service I would recommend that you do so either when you can leave your house for a couple of hours or do so when the A/C or heat is not on so you can open all the windows and not waste energy.