A. Examine the Emerald's Surface
Here, you are looking for the quality of lapidary work.. As you look over the surface, is it smooth and glass like? This is a sign of a perfect polish. You may see pits or scratches, however, If they are few and not visible without magnification, they will have little effect on the beauty of the gem.

Occasionally, the entire surface of the stone is covered with small pits. While the pits aren't visible to the naked eye, they do effect on the brilliance of the gem. The reduction of brilliance may not be readily apparent, as it requires experience gained through comparing various gems.

At times you may have trouble distinguishing if the marks are on the surface of the gem, or inside the gemstone. To solve this, rotate the gem so the light reflects off the facets. When a facet acts as a mirror, inclusions beneath it disappear, but scratches on the surface are still visible.

The girdle should be polished. If not, it indicates that the gem was cut in a hurry. A custom gem cutter would finish this off. Diamonds are cut different than colored stones because of their extreme hardness. A rounded and unpolished girdle is common on diamonds.
To further evaluate the cutting quality, look at the "facet meets". On a well-cut gem, they form sharp corners and all the facets in a row will be the same size and shape. It is common to see facets that vary in size and corners that don't meet or overlap. If the differences are small, they won't have a significant effect on the beauty of the gem. As the problems increase, the brilliance of the gem begins to suffer.

How sharp are the facet edges? This is an interesting clue to look for. Diamonds, with their incredible hardness, have the sharpest edges. That is a clue to their identity. Harder colored stones, such as: CZ's, rubies and sapphires come in a close second. Softer gems, those below nine in hardness, will usually have slightly rounded facet edges. Once in a while you will come across a custom cut gem with exceptionally sharp edges in a material that is only 7 or 8 in hardness. Even though you may not be able to appreciate all the subtle decisions that went into cutting a gem like this, you can spot the quality of workmanship by the polish, meets, and facet edges.

Turn the gem upside down and look at the culet. It may be chipped. This is called "paper damage" and can occur when gems are carried together in paper wrappers. Again, if it isn't visible without magnification, it won't have a significant effect on the beauty of the gem.
The quality of lapidary work affects a gems beauty and therefore its value. A minor imperfection or two is acceptable, but several examples of sloppy workmanship diminish the beauty of the gem. This is true even if they aren't individually visible to the naked eye.
When you examine a cabochon, begin by judging the polish, just as you would with a faceted gem. Look for any scratches or pitting that will reduce the amount of light reflected from the surface.

The next thing to look for is how even the contour is. A cabochon should have an even curvature to its surface. Look at the cabochon from both ends and both sides. The shape, or curvature, should be a mirror image from side to side. No area should be thicker than its opposite and there should be no bulging.

The second way to judge the shape is to hold the gem so light reflects off its surface. Then move the gem so the light travels across the top. If the surface is properly cut, you will see the band of reflected light glide evenly over its surface. The band of light will begin to snake if there are any irregularities. The very top of the gem is where you are most likely to see this. Often a small area will be somewhat flattened. This is hard to see when viewing from the side, but quite obvious as light passes over it. The fact that light doesn't flow smoothly over this area is why it is considered to be second-rate workmanship. However, if you look closely, that area probably doesn't have as good a polish either.