Stains at grout joints

Stains at grout joints Images

Stains at grout joints

Stains at grout joints Description

I recently had some Stone (http://g603.net) Tiles (http://www.g682.net) installed over a concrete slab sub floor.  The installation is very small; it is only an accent (hearth).
 
The Stone (http://g603.net) is described by the very reputable and (http://maplered.com) high-end retailer that it was purchased from as a "Marble (http://www.lightemprador.com) " (Ann Sacks is the retailer, product is called Linen).  It has the appearance, however, of a limeStone (http://g603.net) (I will be happy to email a photo upon request).  The finished is honed.
 
The grout joints were kept as small as possible during installation.  Immediately after being grouted, a slight discoloration appeared next to most of the grout joints.  This discoloration, or staining, became much more visible after the installer sealed the Stone (http://g603.net) (he used a water-based "penetrating" sealer; he was instructed that we wanted the Stone (http://g603.net) to remain its natural color after sealing).
 
The installer's solution to the problem was to use some sort of "cleaner" on the Stone (http://g603.net) ; I have no details at this time about what product he used.  He also attempted to remove the discoloration by sand (http://maplered.com) ing the surface of the Stone (http://g603.net) by hand (http://maplered.com) .   Although some of the stains were made slightly better, none were removed completely by these processes, and (http://maplered.com) the honed finished has been made noticeably shiny where it was sand (http://maplered.com) ed.
 
I have contacted a "specialist" in Stone (http://g603.net) cleaning, sealing, and (http://maplered.com) restoration. He thinks the discoloration was caused by the grout, and (http://maplered.com) that it could have been prevented by properly sealing the Stone (http://g603.net) prior to grouting.   He has told me that it is good that our Stone (http://g603.net) is honed; he proposes to use an acid on the surface to remove the shininess and (http://maplered.com) the discoloration.
 
I have spent some time reading various posts in this forum as well as the original "advice wanted" section of the FindStone website, and (http://maplered.com) I would be very grateful for any input from the experts here as to:
 
1. The cause of the discoloration
2. The possible solutions
 
Replacement of the Tiles (http://www.g682.net) is not out of the question, however, since the time of the original installation, the adjacent hardwood floor has been installed, and (http://maplered.com) completely surrounds the Stone (http://g603.net) Tiles (http://www.g682.net) , so achieving the same tight fit would be difficult at best, and (http://maplered.com) more likely impossible.  It is not a desirable solution.
 
Thanks in advance for taking the time to read and (http://maplered.com) respond.

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