Hi Allen,
This is something that I am not qualified to make a recommendation on. What I can say is that the question should probably be addressed to a conservator. The characteristics of stone vary considerably. Marble is very soft and porous. Soil tends to sink into the surface. I would be very worried that using solvent that might dissolve the adhesive and actually drive it below the surface of the sculpture. The AIC website has a feature that can help you locate a conservator. I would use it if you don't have someone who comes recommended in your area. http://www.conservation-us.org/about...e#.VLhsxa0tFLM
In areas that I do have some expertise in I regularly find absolutely horrifying and dangerous levels of misinformation usually delivered with a chilling degree of confidence. I wouldn't take any action that directly effects the surface or structure of an artwork based on information found on the internet. PACCIN does have a large number of conservators on our listserv. You might seek some guidance by posting your question there.

http://www.paccin.org/content.php?110-ListServe

Ashley