Surface polishing, either to polish or hone a natural stone can be done. It can also be costly and messy. I would suggest calling granite shops to see what they would charge you. We have done things like this in customers homes. Using something to etch it yourself wont produce the same results as using the correct tools to have the finish changed. It will be inconsistent, and likely make it look dull and etched.

agilborder - Did you happen to find a solution for converting your shiny marble tiles over to a matte finish? I'm just beginning to research how to do the same.