Really? Not to sound doubting, but how sure are you? To date, there is NO evidence what so ever that any bullion, jewels, diamonds, etc, etc, etc was ever aboard Titanic (except for what the passengers had in their staterooms, of course, but all of that is pretty well documented through insurance claims). Any large amount of vauble CARGO would have been claimed through insurance, but there is no such claim.
The only extremely valuble item that went down with the ship was a very rare book called the Rubiyat, a collection of eastern peotry written in the middle ages. The book itself wasn't very rare and it was in fact brand new, but the covers were bound with thousands of precious and semi-precious stones all forming elaborate disigns. It has not been recovered as of this date.
Sorry,
David