I am not that knowledgeable on Tanzanite myself so asked a very reputable lady in the high end jewelery business (she is a patient of mine) for advice on Tanzanite.
She agreed it will almost always appraise for more, but often can find the same deals in US. The best knowledge she passed onto me was that the Tanzanite stone is thermal (temperature) sensitive. Her story was a woman with a huge stone (13 carat) wore a ring to a Christmas party indoors, walked outside in very cold weather to her car a distance away. When she got home had found ring had shatters inside stone. I guess the warmth to cold was too much for the stone? The woman had full insurance on her ring. Perhaps it was unique to the largeness of the stone, but I thought I'd pass on a charachteristic to research on the stone as I have already heard it is a "soft stone, and perhaps now temperature sensitive".
Adventure of the Seas RC April 2008
Carnival Liberty April 2007
Carnival Miracle April 2005
Carnival Destiny June 2001, July 2005
NCL Southward June 1985 Honeymoon!