The conservation list would give you the latest methods and pros and cons regarding cleaning marble.  The following is the info I have on subscribing:

  Mail submissions to [log in to unmask]
  Administrative matters (file requests, subscription requests, etc)
      to [log in to unmask]
  DistList Archives: All instances of the DistList are available
      (both for browsing by whole items and searching for individual
      messages): http://palimpsest.stanford.edu/
  The ConsDir is available at the same site.


 
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