Wow, like pulling teeth sometimes isn't it.

Is marble OK for radiant heat?
I know this is an older thread, but I'd like to answer the original question.
YES.
Now will the installation last? I don't know.
Guess that depends on you answering the above questions accurately so that the people who offer their time on this forum at no cost to the users can form some kind of answer to help you proceed sucessfully with your installation.