With regard to the preservation of stone, I know that there is a
specialist who works with the preservation and conservation of
gravestones. Her name is Lynette Strangstad. I know she did some
work with Historic Charleston on some of their cemeteries after the
hurricane a few years ago. I have heard her make presentations at
conferences on protection measures for stone. I am not certain of her
affiliation or how to contact her, however someone on the list may be
able to advise you.
My other suggestion is that a number of years ago, the National Trust
for Historic Preservation published a book on masonry. Perhaps
someone on their staff could recommend some specialists in the
preservation of stone.
Liz Crowell