A first step would be to see if this gem is set in a precious setting (gold, silver, platinum) There are markings on most jewelry. Most precious gems are set in precious metal. I assume the surrounding stones would be diamond. They will scratch glass. The best way would be to take it to a jeweler or a pawn shop. They will assess its value most often for free, in both cases they will tell you what they think it is worth and what they will buy it for. Precious metal goes for melt value and the stones by karat weight. They will not give you your best price but they will tell you if it is real emerald, diamond or whatever. As far as its origin, there are ways to analyze minerals to determine where they come from but I am not familiar with them. For example, the purest copper in the world comes from the upper peninsula of the state of Michigan. They can tell by the percentage of copper in the sample, where it comes from. Color can help determine an emeralds's origin but is in no way conclusive. Most emeralds come from Brazil and Columbia, prior to the opening of the New World most came from Egypt. Cleopatra was enamored of this jewel.