We installed a automated gas burner system for a client. I built a lid for the burner out of cedar. The home technology guy and myself had a miscommunication and the system automated itself which obviously burnt the lid. We used a white (Mexican) stone for the capstone. It is discolored now. I tried bleach, diluted Hydrochloric acid and pressure washing. The stone is still a pink color. Does anyone have any suggestions? Is a burnt rock a burnt rock?