Quality Grading: Diamond Fluorescence and the 4Cs of Diamonds

Quality Grading: Diamond Fluorescence and the 4Cs of Diamonds

Have you ever heard the term diamond fluorescence? Specialists refer to it often, but do you know what it actually means? Some, but not all, diamonds glow under ultraviolet light. For many buyers this is a non-issue, but collectors are also interested in fluorescent properties. The problem with fluorescence is the fact that it is a greatly misunderstood term. Ultraviolet lamps are used on diamonds in the laboratory to help specialists check diamond fluorescence.


The sun is also a source of ultraviolet rays. This means that diamonds with high fluorescence will also glow under direct sunlight. According to statistics, one out of three diamonds fluoresces. The common color is blue, but some diamonds show other colors, like yellow.

There is, still, some negative sigma surrounding fluorescent diamonds, which started many years ago. Back then; this attribute was considered a negative one in diamonds because it was associated with a lower color grade than the apparent color. For example, a J color diamond might have looked like an H or I color one with high fluorescence. In present times, if a diamond is correctly graded, then fluorescence becomes a good thing. If the fluorescent color of a diamond is blue, this means that it will look whiter under normal conditions.

Does Diamond Fluorescence Impact its appearance?

The answer is debatable. In general, around 10 percent of diamonds show strength of fluorescence which may have a noticeable impact on their appearance. However, the overwhelming majority of diamonds has low fluorescence which does not impact appearance. As a matter of fact, the untrained eye will probably never notice the difference between a diamond with fluorescence, and one without. Interestingly enough, many buyers prefer the look of diamonds with medium to strong fluorescence.

In most situations, fluorescence is associated with the clarity of a diamond. That’s because diamonds with very high fluorescence may display a hazy or oily appearance. This brings us to the 4cs diamond criteria for grading.

The 4CS of Diamonds

Specialists study every aspect of a diamond in order to determine quality. Buyer’s should definitely know what a 4c diamond means, before making a purchase. The four most important characteristics of a diamond’s value are the following:


  • Cut
  • Clarity
  • Color
  • Carat weight

Some specialists argue that there is one more “C” associated with diamonds: Certificates. Let us take a closer look at each of these qualities to understand more about the way that diamonds are graded.

1. The first “C”: Cut

Contrary to popular belief, cut quality refers to the reflective qualities of a diamond, not the diamond’s shape. To better explain this we must explain the uses of the word ‘cut’ in the jewelry industry. First of all, ‘cut’ is used to describe the shape of a diamond –example: emerald cut. However, when we talk about ‘diamond cut’ we are referring to its reflective qualities. This is, arguably, the most important of diamond 4cs.


A good cut will result in spectacular brilliance which seems to come from the heart of the gem. If the diamond is well-cut, light will enter it through one place, and be reflected from one side to the other and back to the eye. A poorly cut diamond will ‘leak’ light from the bottom or sides. There are several parameters that ensure good ‘cut’ quality, including the diamond’s anatomy and graded cut.

2. The Second “C”: Clarity

In general, diamonds have inclusions, blemishes or inner flaws which occur during formation process (synthetic diamonds have little to no flaws). The size and number of blemishes influences the quality of a diamond.


The quality graded descriptions of diamonds include “F” (flawless), “IF” (internally flawless), “VVS1-VVS2” (very, very slightly included 1 and 2), VS1-VS2 (very slightly included 1 and 2), SI1-SI2 (slightly included one and two) and I1-I2-I3 (included 1,2 and 3).

3. The Third “C”: Carat Weight

As most of you may already know, the carat is the unit of weight for measuring diamonds. The size of a diamond greatly influences its price.

4. The Fourth “C”: Color

First of all, the color of a diamond refers to the presence/absence of it within the diamond. Collectors prefer colorless diamonds. They are the most desirable ones because they generate refraction of light or sparkle. The color of a diamond will not change with time.

Solitaire Diamond Characteristics


Judging by the graded qualities of diamonds described above, we can conclude that solitaire diamonds are most likely to ace all criteria. A solitaire diamond is a commonly found on engagement rings, and is preferred due to its incredible clarity and beautiful cut. In general, solitaire diamonds are colorless (which ads more brilliance) and round shaped. When shopping for a solitaire diamond one must take into consideration three of the diamond 4cs: clarity, carat and cut.

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