We handle these jobs the same as with non sanded grout. Never been a problem and they come out great !

From: Randy Frye <rfrye@comcast.net>
To: Stone and Tile PROS Technical Support <sccpartners@stoneandtilepros.com>
Sent: Monday, January 7, 2013 7:45 PM
Subject: RE: [sccpartners] scratched marble installs

The synthetic diamond pads float well over the grout lines. Just let them know you can try that and if you have a problem with the grout scratch the stone you will need to pull out the sanded grout and re-grout with un-sanded grout and use a latex instead of water for the grout mix. 

Good luck,

Randy, CEI Surface Pros

On Jan 7, 2013, at 7:07 PM, john jackson wrote:

i keep getting calls  on brand new marble installs with sanded grout, where the grouting has scratched the marble..All i know is to flatten and repolish the floors, with maybe regouting the floor. are there other options ?