Unfortunately Tanzanite Int'l and Diamonds Int'l are two of the most expensice stores for purchase of either. My earrings I bought at Tanzanite are not worth as much as I paid for them. And I have read of many others having the same problem.
Make sure to get as much information before you go. And take it with you. I know in st Thomas you can get better prices at some of the smaller unapproved stores and just as good of quality.
Star Princess 2005, Sun Princess 2005
Caribbean Princess 2006, MSC Lirica 2006 , NCL Pearl 2007, Majesty of the Seas 2008, Carnival Destiny 2008, MSC Lirica 2009, Carnival Valor 2009,Carnival Legend 2010, Carnival Liberty 2010,Carnival Fantsay 2011,Carnival Valor Feb 2012, MSC Poesia Dec 2012, MSC Poesia April 2013