I have found that when I find an item that is encrusted like that a good soaking in CLR will often dissolve the encrustation. When it is encrusted like that it is primarily calcium and CLR will usually dissolve it. BUT, be warned! if it is a junk ring it will sometimes dissolve or discolor the item as well. In my opinion it could be 10K at best, 10k gold is less than 50% gold and it is the alloyed metals that will attract the encrustation like that. 10K does not survive in salt water environment like 14K and greater does. The copper color you are seeing may just be a discoloration of the 10k or may be copper, had to say at this point. As far as an ID, the ring type looks like a "Nugget Ring" and as far as the gold content, that is yet to be determined. another quick test to determine if the stone could be genuine is that fake stones in junk rings are glued in, real stones in precious metals including silver are set in with prongs or a channel holding the stone in. From what I can see in your picture, I don't see any thing holding your stone in, looks glued, if it is glued the CLR will also dissolve the glue and the stone will fall out. Any way good luck on the clean up. Show us your efforts, I would like to see it after clean up, even if it is junk.
HH
Digger