In part one of this article we covered the first five things to know before buying a diamond. Those five were the 4 C’s: Carat, Cut, Colour, Clarity, as well as Certificate. In part two we cover the last five!
6. Shape
7. Fluorescence
8. Size vs. Quality
9. Polish & Symmetry
10. Girdle/Culet
6. Shape
Diamonds come in a wide range of shapes, but choosing the perfect one is simply a matter of preference. You may see the shape of a diamond referred to as its “cut”, such as princess or round cut, but this should not be confused with the term “cut” as in excellent or very good cut which relates to how well the finished diamond has been made and how well it reflects light.
Main differences between the shapes: Round is the classic shape and generally you can’t go wrong with this choice, and it sparkles (reflects light) the best of all the shapes. Other brilliant cuts such as Oval, Princess and Cushion also sparkle well and are a great choice for something a bit more unusual. The step cuts such as Emeralds and Asschers are more translucent, and have an art deco feel, while the more original shapes such as heart and marquise make a strong statement. In terms of pricing, rounds are more expensive while the other shapes (referred to as fancy cuts) can offer better value.
Below is a diagram of some of the most popular cuts and their names. Each shape has its own characteristics which make it special. To find out more about each diamond shape please visit the education section of our website.
7. Fluorescence
Fluorescence in a diamond is caused by tiny boron particles which glow blue (usually) when exposed to UV lighting. In most cases, fluorescence will not cause any noticeable effects to a diamond. However, they may actually make some lower colours (I, J, K, L, etc.) appear to be more colourless or white. Also, in a few rare cases, diamonds with a strong or very strong fluorescence may have an increased chance of appearing milky (oily or hazy).
GIA grades Fluorescence with five levels:
None (i.e. no fluorescence)
Faint
Medium
Strong
Very strong
The level of fluorescence has no direct correlation to the clarity and colour of a diamond. This means that two diamonds with exactly the same clarity and colour grades can have two different levels of fluorescence.
Diamonds with fluorescence can offer greater value for money mainly due to misconceptions about the effects of the presence of fluorescence. If the diamond is not affected in daylight (oily or hazy) then it can be a good value choice.
8. Size vs. Quality
Unless you’re on a limitless budget (and most of us aren’t!), then choosing your diamond will usually come down to a choice between quality and size. For the best value possible it is advised to purchase a well balanced diamond in terms of quality. This generally means the diamond is well cut and does not show signs of yellowing of colour or any visible inclusions to the naked eye.
To ensure a diamond is on the right side of these important barriers, we advise not to go below H colour and VS2 clarity. However if size is the object, as there is an inflexion point at these levels, you can gain significant size by slightly compromising these levels, and one can find significant value at the I colour and SI1 clarity range, but one has to be careful about the individual diamond as some will be too much of a compromise in quality. A diamond will begin to have a visible yellow tint around I or J. Also, inclusions will almost always be visible at SI2. Staying at or above the recommended limit will ensure that you have the whitest and most eye clean diamond possible, while freeing up the rest of your budget for size.
9. Polish & Symmetry
The importance of polish and symmetry are commonly overrated amongst the buying public, because its highly visible and is one of the few things that intuitively makes sense on a certificate. In reality, grading above Good will not have a huge effect on the sparkle of a diamond nor on the price of a diamond.
Both are graded in terms of Excellent, Very Good, Good, Fair or Poor on a GIA report. AGS uses the same scale, but have added an ‘Ideal’ grade. The polish grade of a diamond describes how smoothly the facets have been polished and whether or not any polishing lines are visible. Polish marks are almost always invisible to the naked eye, and have an extremely slight effect on the brilliance of the diamonds. We recommend choosing a diamond with a grade of Good or better.
The symmetry grade judges how well the facets of a diamond are aligned with each other. Few diamonds are perfectly symmetrical, but differences in symmetry can have a slightly negative impact on brilliance. Differences between diamonds with Ideal, Excellent, Very Good, and even sometimes Good symmetry are hardly noticeable and it is recommended that you choose a diamond with one of these grades.
10. Girdle/Culet
The girdle is the edge of the diamond where the crown meets the pavilion. It is defined in terms such as Thin, Medium, Thick, etc., or as a percentage of the diameter. The ideal girdle thickness is Medium. An important piece of advice is not to choose a diamond with a girdle that is Extremely Thick or Thin, or one that has a wide variation such as Very Thin to Very Thick. It is better if the girdle variation is less extreme, such as Thin to Medium, or Medium to Thick. In addition, girdles with Extremely Thin grades are susceptible to chipping.
The culet is the point on the bottom of a diamond’s pavilion. It can either be open or closed. A closed culet comes to a perfect point and would be graded as ‘none’. An open culet is graded from Very Small to Extremely Large and can be considered a facet. For this reason you might see that a round brilliant cut diamond has 57 facets with the 58th being the culet. When choosing a diamond it is best to go with a Pointed (no culet), Very Small or Small culet because these are not visible to the naked eye. Try to avoid medium, large to Extremely Large culets because they may be visible to the naked eye and can be seen from the table of the diamond.
