1. It's all in the Green
The main difference between an average emerald and an amazingly valuable emerald is its shade of green. The most valuable emerald is a green not found anywhere else in the world of gemstones. It should be intense glowing; not pale, not too yellow and not to blue.
2. Size Counts
The other most important factor in determining the value of an emerald is its size. Emeralds less than one carat are not exceptionally rare, so you should not pay premium for a small emerald. An emerald over 2 or 3 carats, however and the value of it significantly increases. In fact, good quality emeralds over 5 carats will always out-price the best 1 carat diamond.
3. Let it shine
Another thing to look for when buying an emerald is how well it sparkles and reflects light from inside. A stone that does not sparkle at all is probably of very poor clarity. A stone that seems transparent but does not sparkle is a very poor cut. Both of these things diminish the value of an emerald.
4. Humans make them too
In recent decades, man has discovered how to make emeralds in laboratories. These emeralds are "real" in the sense that they have all the mineralogical qualities of earth-made emerald, but they are much less valuable. How to tell the difference:
A. Most branded shops you go to will label these emeralds honestly (using names like "created", "synthetic", "lab", or "Chatham").
B. Too clear to be true. Created emeralds are usually much clearer and more sparkly than natural ones. If you see a very clear sparkly deep green emerald for 69.99, you can bet it's synthetic.
C. A nice large emerald set in silver or 10 kt gold. Jewelers will usually not match a very precious stone with not so precious metal. So, you can check the stamp on the metal to make sure it's at least 14 kt gold (or platinum).
5. Manage the Mark-up
Emeralds, like many precious stones, hold their value through the centuries. But if you want to buy an emerald as an "investment"
