Dear Sharon:
Under normal circumstances I would encourage you to get a good-quality marble repair kit, but black marble is among the most difficult stones to polish, and, more importantly, going by your description, the etching (not a stain) appears to be severe.
Therefore, under the circumstances, your only option is to hire a stone restoration contractor who will have to lightly grind (hone) the damaged area and then polish it up to blend with the rest.
May I ask you now to please read and e-sign our Statement of Purpose at:
http://www.marblecleaning.org/purpose.htm?
Ciao and good luck,
Mauri
Article ID: 1007
Created On: Mon, Jan 7, 2008 at 1:43 PM
Last Updated On: Mon, Jan 7, 2008 at 12:00 AM
Authored by: Maurizio Bertoli [mail@mbstone.com]
Online URL: https://marblecleaning.org/knowledgebase/article.php?id=1007