How do I clean Marble

[GPdiver]

I have found a Mortar from a Dutch Frigate that went down in the early 1800's.
Appears to be Marble. Almost a inch thick.
Been in the ocean for some 200 years upside down coverd in hard coral.
I have been soaking in a bucket of fresh water changing it daily.
How do I clean off the coral? Muratic acid 50/50 mix?

 

[RICHinNC]

I have no clue.....but you might want to go to a cabinet maker that works with marble or a grave stone cutter. Both could clue you in or maybe give you a good price to do it.

 

[octotat]

Any attempts to dissolve away the calcium in the coral (i.e. lime away, muriatic acid, etc) will also dissolve the marble. Both are calcium carbonate, so you've got a tricky situation. You probably want to remove as much encrustation as possible with gentle mechanical scraping, but there again, it would be easy to damage the piece itself. You do want to give this thing months in constantly fresh water though to get the salts out of the pores, or it may disintegrate when it dries out. Do you have a photo of it with the encrustation?