Cut: The Third C in Rating

Bear in mind also that a good diamond cutter can cut a colored stone in order to make it appear whiter than it is WHEN THE STONE IS MOUNTED by doing a shallower cut that's more spread on the point where the facets come together. This will make the stone appear less yellow, again only after it's mounted. This is another reason one should never judge a stone that is in a mounting of any sort.

The cut of a brilliant diamond may be the most singular important consideration in buying a stone within a set price range. Unless one is an expert and feels his knowledge is good enough to override general public consideration, there is only one cut to consider and that is the brilliant cut. Brilliant cut is a modern cut that is a completely round stone designed with 58 facets to maximize light reflection and fire within a diamond.

There are a lot of stones still around which have what is known as a European cut. This cut was done in the 1920's and before and does not compare in value to the modern brilliant cut. The old cut or European cut stones were cut before exact ratios and angles were established and understood by the gem cutting society and, as such, do not maximize the reflecting and refraction qualities of the stone. European cut stones such as those purchased at pawn shops and estate sales, are much harder to resell and do not offer the liquidity of a brilliant cut diamond.

There are other popular modern cuts such as the marquise, the oval and the pear which attract some buyers when designed for jewelry, due to their unique appearance. These cuts do not reflect as well as the brilliant cut and are rarely seen in investment quality jewelry.  Again, the fancier cuts will be on the average much harder to sell (definitely harder to sell to a dealer) than is the round brilliant cut stone.

Fancy cut diamonds have fewer angles cut to what is known as the critical angle and, as such, cannot be as brilliant as a round cut stone. The fancier a stone is, the more it differs from a brilliant cut, the greater the loss in light reflection will be.

Another phenomena to be aware of in fancy cut stones such as pear shapes or marquise shapes, is something called the bow tie effect.  This is a dark, cloudy area across the upper portion of the table on these stones. It is a quality inherent in the cutting and looks like a cloudy bow tie across the reflecting portion of the table. This obviously lowers the value of the stone considerably and, if one is thinking about a fancy cut stone, this effect should be taken into consideration.

Fancy cut stones have only two bottom facets as opposed to the eight found in round cut stones to reflect the light back. While they still may appear to be fairly brilliant, the refraction, the fire of the stone, will suffer critically. This loss progresses from the marquise cut through the straight cuts such as the emerald cut diamond. These straight cut stones suffer a great light and fire loss and are not nearly as valuable as the same stone would be cut in a brilliant cut.

Source: Video Vindicator, 1992, BBS.