Overeasy:
I believe it was Blackbeard's "mentor" Benjamin Hornigold who fished up silver coins from the 1715 wrecks. Readers may recall in the classic Treasure Island by R.L. Stevenson, the parrot Cap'n. Flint learned to say "Pieces of Eight! Pieces of Eight" because she was there during that salvage and so many coins were brought up that is what she heard all day long.
I high recommend Robert E. Lee's biography of Blackbeard (No - not that R.E. Lee! Another one!). It exposes many of the myths - and is reliable because he used first-hand accounts, including court records. He proves, to my satisfaction (and his as well, since he wrote the book) that Blackbeard was basically murdered for political purposes after he'd retired. Not that he was a nice guy or anything, but those are the facts.
Good luck to all,
~The Old Bookaroo
2.0: It appears Blackbeard's flagship has been found. But that's another story...