I know it is hard to guess without a picture but I have a ring with a color change Alexandrite that is 3/4 of a cm x 3/4 of a cm. It is a square "Emerald Cut".

It changes from a clear blue about the same color as the "Check Spelling" button on Y!A to a deep purple in artificial light.

I’m not sure if it is natural or artificial.

So my questions are:
1. Is there any way to tell if it is natural or artificial?
2. What would a stone that is 3/4cm X 3/4cm, emerald cut be in Carrots?
3. If I were to want to sell it, where would be the best place to go? eBay? A private Jeweler?

I understand that this is 100% a guess, but ANY estimate for either natural or artificial would be greatly appreciated.

http://www.khazargems.com/color_change_gems.asp

THANKS!!