there is a product called KOOLJOOL (contenti link below)
there is also a heat shield and another type of paste that protects
stones while heating a metal.
I have used the kooljool on gold and on silver to keep heat from
transfering to the stone and have been extremely pleased with the
results. Now, I probably think that it is best, even if you use the
heat shield to get in and get out of the area with your heat. (the
shield does not mean you can sit and heat the area all day) But it
really does help!
julia potts studios