Grading emeralds is often subjective. What one jeweler considers a AAA stone -- a stone of the finest possible quality -- might be an A or even a B to someone else. There are objective standards for judging stones, though, and you can learn them. You can't appraise emeralds with the naked eye alone. At a minimum, you need a gauge to size up the stone and a binocular microscope to inspect it.
How Green Is Your Emerald
The greener an emerald is, the more valuable the stone. The best emeralds have an intense pure green or blue-green color. Yellow-green stones are worth less. If stones have too much yellow or blue in them, jewelers don't count them as emeralds at all. You may have a hard time at first deciding how green an emerald really is. Comparing different stones will help you learn to spot the subtle distinctions.
Clarity and Quality
In gem-speak, an "inclusion" is anything that interferes with light passing through the gem, such as a small bubble or a crack. Don't worry if you find a visible inclusion -- only small emeralds have perfect clarity. Large emeralds all have inclusions visible to the eye: a AAA emerald won't be as flawless as a diamond of the same caliber. If you spot a fracture, that's a bigger problem, as fractures make gems vulnerable to breaking. That might be fine with a pendant, but a ring has a high risk of banging into surfaces.
The Cutting Edge
Judging an emerald's cut is tough because there are so many designs. The first thing to study is whether the cut is symmetrical or unbalanced to one side. Then use your microscope to look for pitting, scratching or dull areas -- signs it wasn't cut properly. The facets should be crisp and meet in a point. A well-cut emerald reflects light so that the gem sparkles. Gem-cutters can reduce the number of facets to make a light gem seem darker, or add facets to make a darker gem brighter.
Keep Your Eye on the Carat
Size isn't a measure of quality, but it will affect the emerald's price. If you buy a one-carat emerald, you'll pay more than for a half-carat gem of the same quality. Even if a small emerald is AAA, a larger stone that's only AA may sell for more based on its weight. Emeralds range in size from a fraction of a carat to hundreds of carats. Popular jewelry sizes run between .05 and 1.5 carats.
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