tanzanite stone help!!!

[Caponekennels]

I have a 3ct loose tanzanite stone round in shape. I took it to a jewelry store to sell it and they said they would give me $500. I don''t know anything about this stone so I took it to get appraised at 3 different places. They said it is a AAA tanzanite (don''t know what AAA means). How much is it worth and what''s a good asking price so I don''t get ripped off? Also, would it be smart to keep it...will the value go way up? I don''t know how to post a pic of it but I can email pics so u can see quality to help me better

 

[Caponekennels]

The color is dark violot and the is absolutly no chips or scratches if that helps

 

[Barrett]

I wouldn''t trust a jewler to give it a AAA rating..really needs a gem lab to do that..something like 1% or less of all tanzanites that come out are graded AAA and it seems as if everyone has one..it''s a term widely tossed around to denote a TOP color stone..really needs a gem report to to say if it is or not