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Beyond The 4C's of Diamond Grading

When choosing a diamond, it's important to look at the four Cs: Color, clarity, cut and carat weight. However, that's just part of the process. Go beyond the four Cs with diamond girdle, polish, symmetry, culet and fluorescence.

Diamond Fluorescence (None, Faint, Medium, Strong, Very Strong)

If you have ever stood under a blacklight, then you know that certain lights make white colors brighten up and even look like they are glowing. The same principle applies to Diamonds, and how a particular diamond responds to UV light is known as fluorescence. When a diamond is evaluated, one of the key characteristics might be its fluorescence.

Fluorescence is the total amount of light that is visible when a diamond is exposed to UV rays. Under ultraviolet light, roughly one in three Diamonds will look blue and glow in varying degrees of brightness. A diamond with a very strong fluorescence rating will be bright in UV light, while a none rating means the diamond will appear dark.

Strong or very strong fluorescence may detract from the overall price of a diamond, but only slightly. Generally, this has little to no bearing on a diamond's cut, color or reflectiveness in normal lighting. It's up to each buyer to determine whether high fluorescence is a drawback in any way.

Diamond Polish (Excellent, Very Good, Good, Fair, Poor)

When you polish a table or a piece of silverware, it is a relatively simple and quick process. Polishing a diamond, however, involves a lot more than just a cloth. Diamond polishing is done at the same time that the diamond is cut.

A trained diamond cutter uses a polishing wheel, which is similar to a sanding machine, to polish the diamond. The polishing wheel uses actual industrial-quality Diamonds to polish a loose diamond. In rare cases, especially valuable Diamonds can be polished by hand rather than by machine, but this is the exception rather than the rule.

It takes skill to polish a diamond perfectly. When a diamond is polished well, there won't be raised streaks, ridges that you can feel or indentations across the table of the diamond. An excellent diamond won't have any of these polish imperfections. Working down from excellent, the polish rating of a diamond can be very good, good, fair or poor.

Diamond Symmetry (Excellent, Very Good, Good, Fair, Poor )

In nature, symmetry is associated with beauty. Even in human faces, symmetry is a desired feature. The same is true for Diamonds. A diamond that is cut and shaped symmetrically is more valuable and considered to be more beautiful.

To the unaided eye, diamond symmetry may not be immediately visible. Ideally, a diamond would have perfect alignment of the crown of the diamond, or its top, and the bottom, or its pavilion. If a diamond isn't cut symmetrically, then its facets won't reflect light as well, and it won't look as brilliant or as sparkling.

A diamond with excellent symmetry is cut perfectly. The facets on the Diamonds will shine as brightly as possible, maximizing the appeal of the diamond. In descending order of symmetry, Diamonds can also be very good, good, fair or poor.

Diamond Culet

The top of a diamond, or its table, is the large flat surface that most people see first. At the base of the diamond, where the various facets of the pavilion meet to form a point, there is the culet. In some Diamonds, there is no culet. Instead, the facets meet at a point perfectly.

If the culet is small, then it can't be easily seen when you view the diamond from the top and admire its table and surrounding facets. If the culet is big, then it might take away from the diamond's shine and value. That's why a diamond culet can be rated as none, if there is no culet at all, or very small, if the culet is minimal. As the culet size grows, it might be classed as small, medium, slightly large, large, very large or extremely large.

Diamond Girdle

Think of the girdle as the belt connecting the crown of the diamond from the pavilion. The girdle is the thin perimeter around the diamond and its widest point. A diamond girdle can be rough, faceted or even polished.

The girdle of a diamond is rated based on its thickness. The categories are extremely thin, very thin, thin, medium, slightly thick, thick, very thick and extremely thick. However, it is not ideal to have a girdle rating on either end of the spectrum.

If the girdle is too thin, then it is more likely to break. If a girdle is too thick, then it might make a diamond appear smaller than it really is. The categories in the middle tend to give the best proportion for a diamond's durability and appearance.