To get the most beautiful diamond we believe the 4Cs should normally be prioritized in this order: cut, color, clarity, carat.

so let’s start with cut

When seeking beauty in a diamond we consider cut to be the most important of the 4Cs for you to focus on as it determines the way light meets your eye in three ways, brilliance, fire and scintillation…

  • - Brilliance is the total light reflected from a diamond.
  • - Fire describes the dispersion of light into the colors of the spectrum.
  • - Scintillation describes the flashes of light, or sparkle, when a diamond is moved.

In evaluating diamonds, cut refers to the stone’s proportions, symmetry and polish, not its shape. If you look at the side view of the standard round brilliant you’ll see the major components are, from top to bottom, the crown, girdle and pavilion. Round brilliants have either 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion known as the culet. The large flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. A wide range of proportion combinations are possible and these effect the stone’s interaction with light.

Diamond cut chart

Cut is a very tricky subject that is often over-simplified when presented to the consumer, even (by necessity) on the very best certificates. This simplification obscures the differences in how each stone ‘greets the eye’ (known as ‘faces-up’ in gem jargon).

The GIA, fortunately ever conservative, avoids over-simplifying the complexity of describing excellence in cutting. They refuse to put a ‘brand name’ on cutting, eschewing terms such as ‘ideal cut’. Thus the best cut stone available is the one we at stuart moore call ‘triple ex’ (a GIA certificate grade of ‘excellent’ for polish, symmetry and, most important, cut grade).

Cut grade chart

So how is the grade of cut determined?
Cut is a combination of each stone's proportions, measurements, angles, faceting accuracy and polish. For round brilliant cuts only, there are now criteria (thousands of computer-modelled angles and measurements) from which cut-grade can be determined and GIA certificates, issued since january 2006, do so.

Simply put, if a round brilliant diamond is cut to those specifications (excellent or very good) it will be wonderfully brilliant. If not, it will be less so. While a stone may be a top color or clarity and as large a carat weight as anyone could wish for, if the cutting isn’t beautiful, the stone will lack some brilliance, fire and scintillation, thus some of its ‘life’.

Although this data is obviously available to cutters, many (even most) stones aren’t cut to these specifications. This is due to commercial rather than gemological (beauty) reasons. Consumers like to hear "1 carat" or "2 carat" so cutters give them exactly that, by cutting stones too deep. This makes them weigh more, in effect sacrificing beauty to get a 2 carat out of a piece of rough that is the right size for a beautifully cut 1.85 carat.

So, what is best for the cutter is not necessarily best for you (be sure to see our ‘size versus weight’ video on this subject).

Since we’ve always thought beauty was a big part of the point of buying a diamond, we ask a simple question; once this size versus weight thing has been explained to consumers why would anyone buy a less than perfect cut?

The answer is ‘size versus weight’ is not usually explained very clearly; instead budget is the focus. Of course budget is important but it is usually possible to get top cutting and find another way to stay on budget (for example, see our texts on short weights and fluorescence). We can help find that balance but what you don’t want to buy under any circumstances is a stone that’s too deep (or too shallow) as they lose light (life) as shown here…

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short weights

When taking delivery of one of our rings, customers often tell us that the diamond they chose ‘loose’ (unset) not only looks much larger than when they selected it but, in our design, it also has more ‘presence’ than the same carat-weight in traditional settings they’ve tried elsewhere. So, in considering budget, we suggest changing your approach from ‘standard’ rings with stones chosen by ‘carat weight’. Rather, we suggest thinking about rings by ‘design’ and stones by ‘tenths of millimetres’. Doing these two things will give your ring more ‘bang for the buck’ as the design emphasizes the stone (instead of just ‘holding’ it) and, by considering buying ‘short-weight’, the diamond could cost considerably less. So what is short-weight? Short-weight is a diamond that weighs slightly less than the well-known markers (1 carat, 1.50 carat, 2 carat etc). The diamond market has created ‘per-carat’ price bumps based on these arbitrary weight changes that create major price increases for minor millimetre changes. Let us explain … Take three diamonds of exactly the same grade of cut, color and clarity. One weighs 1.70 carat, one 1.85 carat, the third 2.00 carat. Typical market prices for these stones are: the 1.70 carat costs $10,000 per carat = $17,000 total cost. The 1.85 carat costs $10,500 per carat = $19,425 total cost. The 2.00 carat costs $12,500 per carat = $25,000 total cost. So the increase of .15 carat between the 1.70 and 1.85 is a rational $2,425 ($160 per point). But exactly the same difference between the 1.85 and the 2.00 costs $5,575 ($370 per point!) What do you get for this money? Less than two-tenths of a millimetre in the stone’s diameter. We consider the 1.85 to be the best value of the three stones because it is just ‘short’ of the 2.00 per carat price bump (short-weight) so is seriously less money (but only a tiny bit smaller) than the 2.00. In fact many (most?) 2.00 carat stones are no bigger in diameter than this 1.85 as we show in our ‘size versus weight’ video. Let’s be clear. Two tenths of a millimetre is noticeable if you compare the two stones closely, side by side, but it is a rare jeweler (let alone consumer) who could tell them apart if held at arms length. It is our contention that short-weight is the very best way to get near-enough the size diamond you want, at your budget, without compromising beauty in any way. By the time you set it in one of our designer rings no one but you will be aware that your 2.00 actually weighs 1.85. But there’s a catch! There are way less short-weights on the market than full-weights. As we say in our ‘size versus weight’ video, imagine you’re a cutter with a piece of rough measuring 7.9mm and have to choose what stone to cut from it ……….. If you cut for beauty you’ll get a knockout 1.85 selling for $19,425. If you cut for weight you’ll get a too-deep 2.00 (which would be less brilliant). It will sell to an uninformed buyer for, say, $23,000 instead of the $21,000 it should sell for or the $25,000 a properly proportioned 2.00 would cost. Many people buy the $23,000 stone thinking it’s a good deal, believing it to be the same as the $25,000 one. Wrong, they’re actually paying $2,000 too much for the $21,000 stone and getting a less beautiful diamond. So, sorry, no prizes for the answer to how many more 2.00s there are on the market than 1.85s. The cutter cuts what the market is asking for, weight, not beauty. That said, our diamond specialists are there for you. Although there are way less short-weight stones out there of any size, they are available with a bit of patience, and we have a great record of getting them out of hiding! The other per carat price bumps are: .50 carat, .70 carat, .90 carat, 1 carat, 1.5 carat, 2 carat, 2.5 carat and then it jumps every half carat.

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fluorescence

Have you ever been in a club where all the white shirts and blouses are so white they’re almost blue? That’s ultraviolet light and some diamonds react to light in a similar way.
From a practical point of view this means fluorescence can be used to ‘confuse the eye’ by adding this ‘blueing’ phenomena to what you see. This can be useful as it can make an ‘h’ color stone look like a good ‘g’ which is a neat budgetary play.

Diamond cut chart

The bottom line? While the recent advances in GIA certificates mean you are pretty safe in assuming a round brilliant cut will look beautiful if it has an excellent or very good rating from the GIA, there is no such assurance at all when selecting any other cut-grade stone.

To get exactly the right cut stone, either online or in-store, we can help you. If you’re buying online, we suggest going to our help section to speak with one of our diamond specialists who will get back to you after ensuring which stones pass their cut test (and they have great eyes!).

If you’d like to personally examine and compare several stones yourself, click on our 'free hotel offer'. Make an appointment to come to any of our galleries and we’ll help you select the right stone over a glass of champagne as well as contributing our bit to make this big day a romantic interlude.

So that’s round diamonds, now to other shapes…

For fancy shape diamonds (everything but round is called fancy shape) there are no measurements, angles or relationships yet available to safely determine cut grade. Even stones that have great grades for symmetry or polish are often ‘dark’ as the cutting proportions are wrong. There are literally thousands of combinations a cutter could choose in cutting a fancy shape diamond so they vary wildly in the way they ‘face up’ (we’ve seen fancy shapes weighing 4 carats that are smaller than a 3 carat). If you haven’t already done so, we strongly recommend taking a few minutes to view our two short videos, ‘size versus weight’ and ‘compare’ if considering buying any fancy shape.

Take us up on our 'free hotel offer' to visit one of our galleries and view a selection of fancy shape diamonds (by appointment) chosen especially for you. Or, if that’s not possible, our diamond specialists can help. Tell them your wishes and budget and they’ll get actual stones in front of them, sort the wheat from the chaff and phone you to discuss your options. Allow about a week for the process.