Diamond Grading - The 4Cs
The 4C’s – Carat, Color, Clarity and Cut – are the global standard grading system that provides an objective way to assess and describe the quality and value of a diamond.
By considering these four factors, buyers and industry professionals can accurately evaluate and compare diamonds to help make informed decisions about their purchase or appraisal.
Specifically, the 4C’s all contribute to determining the value of a diamond. Diamonds with higher grades in the four C’s, such as excellent cut, colorless color grade, higher clarity, and larger carat weight, tend to be rarer and more valuable, resulting in a higher price. Conversely, diamonds with lower grades in these categories may have a lower price due to lower rarity and desirability.
The weight of a diamond is measured in carats – one carat (1 ct.) equals 0.2 gram. The term ‘carats’ comes from the ancient use of carob seeds to measure the weight of diamonds.
Today, we have extremely accurate weights, and we know exactly how much a stone weighs.
The size of diamonds has a huge influence on the price. There are major breakpoints in pricing at 0.5 carat, 1.0 carat, 1.5 carat, 2.0 carat etc.
For instance, diamonds with a carat weight of 0.99 ct. are much cheaper than a stone weighing 1.01 ct. The same goes for all the other breakpoints.
A brilliant diamond of 1 carat is approximately 6.5 mm in diameter.
Clarity describes the number of inclusions in the stone. Inclusions are impurities inside the diamond, and blemishes are impurities on the surface of the stone. They could be polished away; however, that would reduce the carat weight.
GIA, the diamond grading standard, use the following terms:
- F for flawless – There are no inclusions or blemishes under 10X magnification, observed by an experienced grader.
- IF is an internally flawless stone showing no inclusions when examined by an experienced grader using 10X magnification. However, it does have some minor blemishes such as surface grain lines, naturals or extra facets. This can be removed by repolishing, but that’s rare as we’d want to retain as much carat weight as possible. F and IF stones are extremely rare. You will hardly ever see one in a jewellery store.
- VVS1 and VVS2 are Very Very Slightly Included. These stones contain minute inclusions which are difficult even for experienced graders to see under 10X magnification. In VVS1, they are extremely difficult to see in the face-up view, or small and shallow enough to be removed by minor re-polishing. In VVS2, they are very difficult to see, but a bit more severe. They might be pinpoints, tiny feathers, internal graining, a bearded girdle or tiny cavities.
- VS1 and VS2 are Very Slightly Included. VS diamonds contain small or minor inclusions observed with effort under 10X magnification. VS diamonds typically have small included crystals, small clouds, or small feathers.
- SI1 and SI2 are Slightly Included. SI diamonds contain inclusions that are noticeable to an experienced grader under 10X magnification. Typically, these are clouds, included crystals, knots, cavities and feathers.
- I1, I2, and I3 are Included. Diamonds that fall in the I range contain inclusions which are obvious. You will not even need a loupe to see the inclusions. They might contain larger feathers or large included crystals. In some cases, the inclusions affect transparency and brilliance, and might even damage the stone.
Most of the diamonds in the finer retail stores are in the VVS to VS range.
Normally, I recommend diamonds in the VS1 or VS2 range as the price in this range is very reasonable, and the inclusions are invisible to the naked eye. Even using a magnifier, they are difficult to see
White diamonds are graded using a scale from D to Z where D is the whitest color possible with no traces of yellow. A Z stone contains the most yellow, and after Z comes the fancy colored yellow stones.
By far, the whiter the stone, the more expensive it is.
I usually recommend diamonds in the color H, I or J because they are what we call ‘nearly white’. It’s impossible to see any trace of yellow in them with the naked eye. H/I diamonds are generally really well priced and a good buy.
The cut of a stone is extremely important.
An uncut diamond resembles two pyramids on top of each other, bottom to bottom. The cutters try to retain as much weight as possible, and the diamond must be cut perfectly in order to create the optimal reflection of light. The light has to be reflected off the sides inside the diamond and reflect back through to the top of the diamond to the viewer and not disappear into the stone. For decades, scientists have been arguing about how to get the perfect brilliant cut, and there are few accepted cuts. The GIA has decided that a diamond needs to have exact proportions to reflect light in the best way. When grading a diamond, you consider all these facets and grade them in accordance with the weight and height of the stone.
Cut grades are Excellent, Very Good, Good, Fair, and Poor. I would recommend stones which have a Very Good or Excellent cut grade.
Asscher cut. A square cut similar to an emerald with facets; however, it is more square rather than rectangular shaped. Like the emerald, it has clipped corners. Recently the Asscher shape has become very popular.
Emerald cut. The shape still retains its old world elegance.
Heart cut. Hard to find due to low demand, but some prefer a heart shaped diamond for sentimental reasons.
Marquise cut. Like the emerald, the marquise is a traditional shape. This is probably the fourth most popular after the round, princess and oval cuts.
Oval cut. Very popular for three stone anniversary rings with two matching stones on the side
Pear cut. Mostly used in pendants, the pear shape diamond is shaped as a teardrop and has fairly good proportions to refract light well.
Princess cut. A square cut diamond that has refractive properties close to the round brilliant. The princess is one of the preferred square cut shapes.
Brilliant cut. The round brilliant is by far the most popular cut in the world. With its 57 facets, it has the best angles to allow for maximum brilliance.