fire damaged rock

Quoted text begins.Do you have any advice about cleaning stone that is heavily fire damaged?
End of quote.

Tomas: A lot of variables and unknowns here, but it is possible to clean
the stone without abrasive media using alkaline-based chemicals with a
pressurized water rinse. Depends on how heavy is the carbon deposition, how
hot did the stones get during the fire (interesting things can happen
chemically to some stones when heat is added to the equation). There are
also specialty restoration abrasive systems that use media tailored to the
mOH of the substrate. Check with the local stone restoration contractor in
the area or go to: http://www.traditional-building.com/rte.htm for
Traditional Building's reference service, one of several.

Good Luck!

Chaz