I hope someone can help me solve the mystery of the discolored limestone. It was a beautiful chalky white prior to grouting and post-grout cleaning. Now it’s a blotchy pale orange, and has a hard plastic texture. From my understanding, the masons cleaned the stone with only water after they grouted. But I’m wondering if there was some sealer or other chemical residue in the buckets or sponges that may have caused it? It‘s had plenty of time to dry as it’s been installed over three months now with no changes in color or texture.

The stone rep and contractor both thought it could be moisture from the mortar or grout. So two stones were removed and placed in the sun for a week. There was no change in the color or texture. And the discoloration was only on the top surface, not the grouted sides or back. We have tried

poultice and acetone with no luck either. Our contractor says it will be replaced if we can’t find a solution. But I would prefer to try whatever we can before we go that route. I also want to find the cause so we can prevent it from happening again if replacing the stone becomes necessary.

Would love to hear any ideas or suggestions! Thanks!