Diamond shapes and cut grades - why is this important and what is better?

Diamond shapes and cut grades - why is this important and what is better?

This week we are looking at diamond cut grades and shapes. Why is diamond cut grade, symmetry and polish important and how does this affect prices. This in itself is a deep dive subject but I will cover the basics as best possible to give more insights as to a standard explanation that you will normally get. As per the following 2 images of a diamond certificate  Round Brilliant cut diamonds get graded for it's cut quality in 3 areas namely: Cut, Symmetry and Polish. You will note that fancy cuts (any diamond shape other than a round brilliant cut ) only has Symmetry and Polish.


Now how do they judge each variable? Well a lot of factors get taken into consideration with certain tolerances for every grade this is mostly the relation in % of every facet to one another , the depth ratio the top table ratio to the overall diameter, angles of the facets, thickness of the "centre line" of the diamond ( girdle) between the top( crown) and the bottom (Pavillion) in ratio. So diamond cut grade is determined by ratios, angle degrees in percentages to one another. The Laboratories have certain angle variance tolerances to consider on the overall combination of all these % angles and ratios. The closer the angles all are in the ideal ratios and angles the higher the cut grade or scale ranging from Ideal/Excellent to Very Good , Good, Fair and Poor. See the diagram below:

Now the laboratories all have their own scales and slight variances in their respective threshold exist e.g. as per above AGS lab has 6 levels , GIA has 5 and HRD has 4. In all the main levels are very similar with Ideal/Excellent in very tight scales to Very Good that is close in it's tolerance, then Good with a much wider tolerance and Fair and Poor with even wider tolerances. The scale below in my experience shows the spread pretty well in terms of strictness of the tolerances. The cut grade shows the diamond cutter degree of accuracy and craftmanship on the particular diamond hence the skill level and time spend on cutting a particular diamond in a sense. Also the amount of rough diamond lost also plays a part in this that we will touch on later. All these individual factors influences the pricing.

Symmetry is the second factor and that is basically the alignment of all the facets with one another and accuracy in sizes to one another. Extra facets as small as they are, girdle thickness variation or diamonds not 100% round usually not even noticeable with the eye impacts the symmetry grade. With round brilliant cut diamond the cut grade and symmetry usually runs close to each other as overall cut grade takes into account the symmetry and polish grades. With fancy shapes the ratios of the facets, overall alignment of facets , proportion and ratio of the diamond in length , width and depth all goes into the assessment of the symmetry grade by the diamond grader, this allows for some subjectivity as the overall appearance is taken into account in fancy shapes. Below is a round brilliant diamond facet breakdown that is considered and compared with one another in their alignments and how well the compare to one another:


Polish is the 3rd factor and that is part of the finishing process of a diamond. Here polishing basically grades how clear the diamond is polished i.e. how many and how obvious is polish marks left on diamonds. Yes diamonds can have polish marks see the following example:

So basically the better and cleaner the polish the sharper and better the reflection through the diamond and that promotes more sparkle and fire.

Right so what does this have to do with the appearance? Well as you can guess a lot. A Diamond will only look like a proper diamond if all the facets, angles and ratios work together once light enters through the top of a diamond and "bounce" around inside the diamond and reflects back out through the top of the diamond. The better the reflection the more striking the diamond appears and less "deadspots" as light does not escape through the side or bottom of a diamond as it enters called light leakage. Note all diamond and gems will have a degree of leakage but the better the cut the less. Below diagrams illustrates this concept:

So this is why cut grades are important because the cut grade is what the eye sees in terms of brilliance and sparkle. Note for fancy cuts I would look at the symmetry as an indication of the "cut grade". Now everybody would say well go only for excellent grade right? Well not so fast- Remember I highlighted the tolerances that they use to judge, to a degree subjectively, the grade? Now the higher up the scale the more technical the differences become. Now looking at the above pictures the big swings are between excellent , good and poor. So as with the factors in colour, clarity , weight look for the in betweens if you want to get more out of your money. I know a diamond that has excellent cut, symmetry and polish referred in our trade as EX EX EX demands a premium as it should, but little sweet spots can exist where you get a Very Good (VG) cut grade and still excellent or very good symmetry and polish depicted as VG EX EX, here you can find a good price drop for technical reasons. The level between Ideal, Excellent and Very Good is very tight and small minute technicalities can throw a diamond one down the scale. Here you can win. Also for experts we can see compared with one another a change but for most people they probably won't notice a difference between the top 20% percentile of grades ( Excellent and Very Good range). Now one can go even further and I am also happy to look into Good cut, it has a much wider tolerance so you can get not so nice Good cuts but know what too look for. Below diagram show the differences in these major scale grades:

Now next to each other and magnified you see parts missing or not aligned etc. In real life they look way closer to eachother never mind seperate from one another. I would like to always try when looking for a good (not perfect) quality diamond to find a top side Good cut graded diamond as they trade as bigger discounts but can still off the eye to public look excellent! Main issues to look and compare is the depth as a lot of these are cut deep so the diameter of the top vs a better cut stone noticably smaller when comparing , sparkle is usually there I might look for a Good cut grade with Very good symmetry and good polish to give an idea. These one's I will definitely want to see beforehand and make sure they are close to top view diameter to a better cut grade. If ordering online make sure you can return as a lot of online stock can be the lesser preferred Good cuts that are being sold off cheaply. I would for engagement rings etc. stay away from fair to poor cut especially Round Brilliant. It is not worth the drop in price and more so drop in the look.

Fancy cuts would be even more subjective in their assessments and they tend to have more Very Good and Good symmetry grading. Here these grades should serve on well and again don't jump under those grades as they will be noticeably worse in appearance. Here are all the fancy shapes: 

These are the major fancy shapes there are lots more but for a center stone I would say these are by far the most popular. Big trick with fancy shapes(and round brilliant to an extent) is to not buy diamond where all the weight is in the middle( stomach line) or buldging diamonds with fat rounded out bottom pavillion, basically a lot of the "carat" weight is caught in the depth of the stone or thickness and the face (viewable) size is smaller or not in ratio. This causes wasted money as there is no real appearance value in having the fat diamond. Rather then go for a lesser carat weight but better spread of the top view, it will give you the same look as the bigger one but will cost less. Hey if you want a carat weight and save a bit then use this to negotiate a better price. In the end it's about what you see and like, factors like this can be build into a cheaper price and should just make sure it is by comparing the correct diamond variables to one another.

Last part on this brief overview is why does excellent or very good grades cost more? See the following image to show how cutters cut diamonds from rough diamonds:

So without over complicating the better the cut the more of the original diamond rough is lost. This is one reason why better grades are more expensive and why all diamonds are not cut excellent because in a way all diamond could be cut excellent. So this is why people cut diamond fatter, shallower, deeper etc. is to get the most out of the rough or a lot of times hit weight thresholds as explained in my previous blogs to get higher prices. A cutter would most likely rather want a 1ct diamond good cut that is is little deeper than a 0.95ct excellent cut. A lot of factors like colour and inclusions play a role but basically they will cut to get the most out of the rough dollar wise. Round Brilliant diamonds are approximately 20% more in price vs a comparative fancy cut. Reasons are the loss as seen above from rough is much higher, more facets and stricter symmetry is needed to get the look and higher skill is needed. Fancy cuts can also be cut out of all types of diamond rough crystals whereas round brilliant cut need certain quality rough to cut from. Round diamonds are also more stable in demand of over 80% of diamond demand where fancy cuts are more subject to fashion trends. This all plays a role to demand a premium on round brilliant cut diamonds.

So why is this important and what is better?

The facts about why this is important says it all - the better the angles and ratio in a diamond the more fire, sparkle/brilliance and life it has- this is obvious. The send question- What is better, depends on how you approach cut grade. Better in terms of technical , overall appearance or budget vs value add? Technical if factual Ideal/Excellent cut will (in most parts) based on this one variable give you the perfect/ near perfect appearance.

Appearance can be a combination of lots of factors but what looks good? A lot of times your eye catches other factors that you like and stand out more e.g. the florescence, luster , clarity or colour aspects combined with the cut grade. Appearance is subjective and in the eye of the beholder and different sparkle based on angles and even jewellery setting can play it's part. Antique style jewelry you would want to look at off "perfect" ideal proportions that will give the look so a good/fair cut can work well to fit the motif. Remember the cut grade is based on perfect alignment and specific defined ratios from the grading institute so what is excellent to you in your eye? A-symmetrical or perfect symmetry?

As far as budget vs value add goes you can see, depending on your end goal in jewellery what will work best. The best cut isn't necessarily the best option. However most modern style rings the go to is the better symmetry. Here I would from a value vs budget perspective go for the combinations and mix of grades that serves my personal tolerance from a viewing perspective. If the diamond look visually off to you it's obviously a no go. When weighing up a EX EX EX diamond to another grade I usually, assuming a noticeable price difference, would aim for a Very Good(VG) cut grade in all three areas or mix of EX VG- there is usually >10% price difference and then the difference in the grade is technical reasons as the tolerance is so tight. Any gems in the good (GD) range I would entertain if they just missed the VG cut , I noticed these will usually have either cut grade or symmetry VG and other one GD that is a great indication. The GD range also trades at more discount than the VG en EX grades so worth comparing. Just again , it depends on your preferences and tolerance, so always physically look at diamonds in this category (assuming you want more symmetrical diamond) and compare with one grade up. If the difference is really noticeable then go higher or look further but if it looks great on it's own or holds itself against the higher grade then go for it as the lower price is worth more than the difference you see. As I always say use the money movers where it is visual - rather then go for a bigger diamond in look with the slightly lower cut grade because the bigger face you will notice.

So deciding what is better is a personal choice, know what the jewellery piece end goal is or communicate it with your seller so they know. If you want the picture perfect diamond go EX and VG they all are in terms of cut in the top 20% so that's an A grade with the premium vs GD grade! If you want more value consider VG and GD with a combination, I would first visually look before committing if all areas are GD due to the wide tolerance in this scale grade. There are great deal to be had here so worth entertaining with doing more due diligence work.    

I hope this gave some insights into the cutting world of diamonds and how it all plays a role to get to the money value of a diamond; simple end price yet very complex variables playing into it. Next week I will dig into who grades diamonds and differences in them so my focus will be on certification.

How does Diamond colour work and how to choose the best option

How does Diamond colour work and how to choose the best option

Last week I started the April Diamond month looking into clarity and broad view of some elements to look at when buying diamonds. The following blogs will focus more on the variables in diamonds, how they work and how to choose the best option. This blog will focus on diamond colour (color) and how it actually works and how to choose.

Now for a lot of people the focus is usually on weight; How many carats does it weigh? Without looking too much into other factors. Colour plays an important role in the pricing of a diamond just as much as the weight factor. Every jump in colour can shoot prices up 5-20% roughly depending on where on the colour scale the diamond is. This can obviously make a huge difference in the pricing if you are working in thousands or even tens of thousands!

So let's look at how colour works when graded by the laboratories. A lot of places use the GIA colour grading scale , see attached GIA Color Grading Scale. 

There are 5 main categories diamonds get classified in as seen above. Note all diamond you see here as view from the side angle. This is because diamonds are mainly graded based on the side view colour and not the top view. There are technical differences that distinguishes say a colour D from an E from an F in a category like colourless, that is to an extent subjective. The main thing to look at here is the differences between categories versus one colour grade in a catergory. The catergories are largely there because this is where you will notice a difference (to an extent) between diamond colours. The best way to explain this is by imagining looking at a loose diamond from the side and top: Colourless diamonds(colour D-F) under a daylight light equivalent will show no undertone/tint of colour from both the top and side view. Near colourless(G-J) under same conditions will show no colour from the top but some tint/undertone from the side. Faint Yellow(K-M) will show some tint from top and side. Very light Yellow and Light Yellow will show obvious tint from top and side more as you get closer to Z. The following is another chart to show the gradual colour change bearing in mind the big jumps in catergory criteria.


Now the question is what to choose?

Like most things in life it depends on the diamond size, shape, setting etc. but mostly the following is the way I go about it:

I have always been looking for where the value lies for myself and clients throughout the years. Now as I explained the difference in appearance becomes more noticeable when you jump over to another category as the colour you pick up with your eye can be noticeable especially if you put two diamonds side by side. Given that prices move 5-20% on a colour every jump I tend to focus on the two colours at the border of a catergory eitherside, because jumping around the middle of these categories is really not helping the visual aspect and not your wallet. Now again here it is relative as a colour D or F will look the same except if you are trained and have exact light conditions in a laboratory. The change is so small that you will also have to look hard to see the difference solely in colour to a H if you are not used to it. The reason is the criteria mentioned earlier of face up / top view being colourless in view. The side view colour changes as that is technically the difference but so what? Nobody looks at the side view of a diamond in most settings. I would rather put my money in a larger diameter size diamond in such a case as that would be noticeable. So based on appearance Colourless or near colorless it is more technical as all will have a white face up appearance.

If you are looking at the Near colourless or Faint Yellow categories more caution needs to be taken. Here prices can move more but for good reason as now the top face up view has a tint or undertone too not only the side. Here I would look into what colour tint the stone has e.g. does it have Yellow (normal) less noticeable, Brown tone (give a warmer tone) bit more noticeable, Grey ( more milky look) or Green (Yes even green tinge exist very noticeable). Yellow tint is subtle enough to get away in white gold or platinum if it is again on the border line between J and K so then not noticeably see obvious colour. Here a lot depends on the colour of the metal being used. Now a lot of Yellow and Rose gold is back in fashion so that's great because the Faint Yellow category's tint gets masked by the metal colour so appears Colourless/White.  Tone under colour M becomes a personal choice as it is mostly obvious Yellow or Brown tint yellow their pricing is also closer as the classification becomes looser until you get to Fancy Yellow (after Z). 

I hope this gives a better understanding of colour in diamonds and what ranges to look for depending on your goals and preferences. I mostly advise on F/G colour if you want the super white diamond, then I-J for a white diamond in White gold or platinum, K-M for a "white" diamond in Yellow or Rose gold with brownish tint diamond for rose gold and Yellow tint for Yellow gold where best value for money on a budget is requested.

Note there are other factors that can influence the look like clarity, cut, tinge and fluorescence that is not taken into account when grading diamond colour that I will write about in future articles.

Enjoy the week and next up will be carat weight you don't want to miss!


Some points to take into account when buying diamonds

Some points to take into account when buying diamonds

Ok so every week I attempt to put something out that assist people in buying high end gems in an informed unbiased manner.

One area I have seen many people in public get burned is with the oh so misunderstood world of Diamonds. Crazy as it may sounds the majority of people selling diamonds are also most of the time just as misinformed.

So the month of April will be the focus on diamonds as it is the birthstone for April in traditional and modern beliefs. I will keep touching on this as it is still one of the big gems sold worldwide and a lot of truth must be told mostly for the good but also for the ugly.

First focus is the well known 4C's - Cut, Clarity, Carat (weight), Colour- if you have shopped for a diamond for more than an online search or store visit you have heard about this. This is all 100% right but this is the limited view of a diamond when buying it even more so if buying it online without seeing it or comparing two similar diamonds. This is also where the "new" 5th C comes in certification i.e. the laboratory report from a gemological laboratory. A lot of people fall into this trap - buying after gaining some knowledge on the 4C's a diamond based on the certificate and without sighting and comparing the diamond with others. 

Certification and how labs certify is not a straight forward process and use technical mostly objective processes to grade a diamond. My attached image is a good example of two diamonds that received same grading. How can this be? Well all depends on the criteria used by laboratories and it differs to a degree as the grading scale everyone is told is not a fixed standard or law but a mere guideline or concept created by the famous GIA lab in fact there are numerous scales of grading a diamond. 

Here is want to give the first example of clarity as per picture. Clarity is normally graded by the amount of inclusions and size of the inclusions also taking into account the amount of relief (basically seeing the inclusions). In this case to the right hand this type of "inclusion" is called a cloud it affects the appearance but from an inclusion point of view is not taken into account to "penalize" the rating , here both diamonds were rated VS2. However these clouds will often be found in the comments or remarks area of a certificate, same for diamond florescence.

It is a big risk to just buy off a certificate even for professionals as a certificate doesn't tell the whole story. Lot of online diamond lists selling cheaply will usually try to move off inventory that has these characteristics as they couldn't sell in the normal market. Always ask what the luster is trade lingo would be excellent luster or milky, is the diamond eye clean i.e. can you see marks with the naked eye or not, although very subjective it is one step more to protect yourself from buying something you don't want and will sit with with a hefty price tag on it anyway for what it is. 

So buying from an actual jeweller in person allows you the chance to see it , compare it and get relevant information just as you would want from any qualified professional. Check the background of the jewelers are they actually qualified or just talk , same with online check and make sure you are in good hands. There is no right or wrong on buying in person or solely online however each method has it's risk and you usually get what you pay but as always there are premiums for buying from certain brands as there will always be. Note that the diamond industry has transformed in the last decade and diamonds are very much a type of commodity so if there exist a big price difference for similar item do proper research and inquiry before committing as most likely there will be a reason.

Remember if you want you can even get a qualified valuator to do a pre-purchase appraisal to support your decision especially on large purchases.   Always make informed and educated decisions besides being prudent it is a lot of fun the more you know! 

If you ever need any information or have uncertainties on diamonds and just need an extra opinion or help , please book an online meeting, call, email or come visit me I am more than happy to help regardless if you want to buy from me or not! I love what I do and want to help the public make the right decision for them.


April 05, 2020 — David van Niekerk