30 cts! That''s pretty big. Such a stone has story...
Where is it from? Any chance for pictures?
As with anything, the value goes all over the place with quality, but even though Tanzanite is available in relatively large sizes relative to other precious materials, 30 cts is still quite allot. Especially round...
Sure I''d do an appraisal. And you should end up with some good advice from the appraiser about how to go about selling the piece too.
I seriously doubt that you have a 30 ct. tanzanite - I don''t doubt you, I doubt that it''s tanzanite. If it is, and it has any color and clarity, it''s worth like about $250,000. (Not an appraisal, an offhand comment) Even a junky one that size would be worth quite a lot. Tanzanite that big is almost impossiible to find.