Is a 1.00ct that looks like a 0.95ct diamond acceptable?

[Garry H (Cut Nut)]

I am shortly adding a new additional functionality to HCA.
It will indicate an approximate apparent or Looks Like size of a diamond. Factors used: relative diameter to the stones weight (math formula calculation), edge or peripheral leakage / light return and symmetry. Diamonds can look bigger or smaller depending on cut.
I envisage 4 relative sizes: Bigger, Big, Small and Smaller (or Very Small).
My question to you'all is this.

The boundary between Big and Small - so thinking about 1.00ct rounds only, I am thinking that any diamond that looks at least 0.95ct size could be called Big. Most stones are 0.1 to 0.15mm smaller than optimal. Half the 1.00ct diamonds listed on PS appear smaller than 0.95ct; most PS vendors list better than average stones.

I remember discussions years back where one of our vendors posted many consumers care more about the magic sounding or name like half carat, one carat, two carat etc than all the hoohaa we bang on about.

A guy knows his girl (and her friends and family) will insist on magic / naming rights “It’s a 1ct diamond, will you marry me”.

So I propose the smallest ‘Big’ 1.00ct diamonds at 0.95ct which are usually +6.3mm diameter (or proportional equivalents for any carat weight), and believe it or not, there are some under HCA 2.0 stones on our PS database!

 

[CareBear]

To the general public it is acceptable because:
- No one even bothers with their stone's actual diameter
- visually a 1.0 at 6.4 vs 6.3 looks about the same size
- it's no secret that a 'just under' carat weight stone costs a lot less, most buyers are aware but choose to pay more to hit the 'magic weights'

I'm a cost savings type of girl, so I specifically asked my DH look for a 'just under' stone when we first got engaged. My current stone is also a 'just under' stone. In the cases where my stone was over the 'magic weight', I make sure the same diameter was not possible by staying 'just under'. Hope this logic makes sense!

 

[Paul-Antwerp]

I remember discussions years back where one of our vendors posted many consumers care more about the magic sounding or name like half carat, one carat, two carat etc than all the hoohaa we bang on about.

A guy knows his girl (and her friends and family) will insist on magic / naming rights “It’s a 1ct diamond, will you marry me”.

Hi Garry,

As far as consumer-motivation goes, I agree that the magic weight of 1Ct will be valued higher by most consumers than a 0.95 Ct.

But I disagree that it is related to naming rights or a girl's (a guy's, for that matter) frickle behavior.

I see it far more related to an entire industry 'educating' for approximately a century, if not longer, that the value of a diamond is determined by the 4 C's. One of these C's is Carat Weight, and consumers are simply reacting to what 'the industry' is teaching them, incorrectly.

Personally, I do not believe that consumers (before 'incorrect' education) care about the small differences in carat weight, which they will find hard to discern. Far more important for them is sparkle and other factors of light performance. For sure, if they are sporting a truly sparkly stone, they will get far more positive comments, and far more 'naming or bragging rights' will be attached to that.

Live long,

 

[OoohShiny]

Hi Garry,

As far as consumer-motivation goes, I agree that the magic weight of 1Ct will be valued higher by most consumers than a 0.95 Ct.

But I disagree that it is related to naming rights or a girl's (a guy's, for that matter) frickle behavior.

I see it far more related to an entire industry 'educating' for approximately a century, if not longer, that the value of a diamond is determined by the 4 C's. One of these C's is Carat Weight, and consumers are simply reacting to what 'the industry' is teaching them, incorrectly.

Personally, I do not believe that consumers (before 'incorrect' education) care about the small differences in carat weight, which they will find hard to discern. Far more important for them is sparkle and other factors of light performance. For sure, if they are sporting a truly sparkly stone, they will get far more positive comments, and far more 'naming or bragging rights' will be attached to that.

Live long,

I think this is exactly the thrust of @Serg's recent postings - how can the industry better measure / quantify / 'sell' the outcomes of excellent light performance? And how can they overcome the engrained obsession with carat weight?

Perhaps it is because carat weight is easily understood - it is a number, one number, and (virtually) everyone understands that some numbers are bigger than other numbers.

Light performance, though? AGS has attempted it, with their number-based grading system, but that doesn't capture the nuances of a given cut, in terms of fire / scintillation / etc...


Anyway, I think I am going Off Topic! lol

 

[gm89uk]

Hi Garry,

I've always thought that true spread should be mm/carat (diameter / carat ^(-3)) which I discussed here to standardise every carat to 1carat

https://www.pricescope.com/community/threads/diamond-depth-are-we-too-strict.239598/

Then you can compare any carat weight and diameter against the 6.3mm or whatever margin you choose. If you have easy access to analyse lots of diamonds on HCA, you could define big as mean + 1sd.

My gut instinct is 6.3 is a bit lenient to be "big" but I haven't analysed this over thousands of diamonds.
https://www.jamesallen.com/loose-di...color-vs2-clarity-true-hearts-cut-sku-2536114

This 62.7% depth 1 carat managed to get 6.42mm.

How about an Bigger, Big, Average, Small, Smaller?
Average from -1sd to 1sd, big small > or less than 1 sd and biggest, smallest 2sd.

Would this replace spread on HCA?

 

[SimoneDi]

I am not sure if “Big” and “Small” are a good choice of words. Perhaps something like, “size spready for weight”,”size accurate for weight”, “size small for weight” would be better.

 

[diamondseeker2006]

6.3mm is small for an excellent cut 1 ct to me. I would find the label "big" for 6.3 to be misleading. I'd start at 6.4 for big.

 

[oldminer]

With everything today revolving around science and numbers, it is very tempting to revert back to using descriptive words for grading. However it is more straightforward to use numbers and let the consumer simply compare facts which they are curious about. Not everyone cares all that much about every last detail, but for those who do care, then it seems best to make the data available for factual decision making. Why make this easily measured factor subjective when it can just be fact driven and numerical?

If light behavior is optimized for a range of surface area within the boundaries of the girdle, then let the tool spell out that range for that weight and shape, then let the calculation show if the stone is within that range of visual size or to what percentage above or below it is. Just give consumers the facts and let them make smart decisions which fit their budget and needs. Many diamonds are not cut for optimal size, but look wonderful. That's no problem so long as the information is available and easily understood. Why be accused of hiding the facts by calling a slightly below best measurement "big" when it could be called -2.4%? (using a 6.3mm versus 6.2mm example diameter)
Let a customer decide if a -2.4% less size means anything at all to them. Might a 2.4% smaller visual size be possibly 4% less money on occasion? Would that justify a designation of "bargain priced"? It is for the consumer to judge, I believe. Maybe a -2.4% stone gives super light return and would be worth somewhat a premium price because of the light return and part of the equation is a tiny bit less visual size. Either way, it is truthful and justified by a free market and informed buyers.

I don't want to make this a ranting complaint because I really believe visual size to weight is a highly meaningful calculation for every shape of diamond where we can compute and report light return measurements or grades. It makes sense to me not to draw arbitrary boundaries which might be seen as concealing facts when it isn't really the intent to conceal, but to advise.

 

[Karl_K]

I honestly don't like the concept all that much for a couple reasons.
Who defines what a 1ct diamond should be?
It can drive people to flat bright stones that have compromises in scintillation and fire potential.
It does not take into account the 3d look of the diamond.
One diamond may look bigger face up but at 30 degrees on the hand another may look bigger.

The reality is that MM size is a compromise in an RB, you have to give up a little to get something in other areas of diamond performance.

 

[oldminer]

If you do it my way, no one is "defining" what to buy or choose. Consumers need facts to make decisions. Thankfully, choosing a diamond is not something that can be done based on a a single result that pleases everyone. Garry isn't suggesting that size to weight is the way to select a diamond or that it is the way to understand the quality and amount of light return. He is saying that consumers ought to understand this additional element in order to make their own best decision. There is a wide range of diamonds and knowing what is going on with each one is seen as an aid to making a choice properly. Doesn't that make good sense?

 

[CareBear]

https://www.jamesallen.com/loose-di...color-vs2-clarity-true-hearts-cut-sku-2536114

This 62.7% depth 1 carat managed to get 6.42mm.

I'm wondering how this can be possible? Meanwhile this stone with a much shallower depth, much bigger table, and with only a slightly higher crown yielded the diameter?
https://www.jamesallen.com/loose-di...-g-color-i1-clarity-excellent-cut-sku-5778159

 

[gm89uk]

I'm wondering how this can be possible? Meanwhile this stone with a much shallower depth, much bigger table, and with only a slightly higher crown yielded the diameter?
https://www.jamesallen.com/loose-di...-g-color-i1-clarity-excellent-cut-sku-5778159

If you read the thread I linked it attempts to explain it. Although there is correlation between spread and depth percentage, it is not absolute, and certain diamond proportions with relatively high depth percentage can have a large spread.

 

[diagem]

I honestly don't like the concept all that much for a couple reasons.
Who defines what a 1ct diamond should be?
It can drive people to flat bright stones that have compromises in scintillation and fire potential.
It does not take into account the 3d look of the diamond.
One diamond may look bigger face up but at 30 degrees on the hand another may look bigger.

The reality is that MM size is a compromise in an RB, you have to give up a little to get something in other areas of diamond performance.

As usual, we are talking rounds only so I’ll just add my humble 2c’s...
I agree with Karl, especially on the bold part.
3D optical effects are as important as diameter size, if not more..., in fancy cuts they are even more substantial but that is for another thread.

In any case, I personally would much rather prefer a 6.30mm with a 17-19% CH than a 6.42mm 14% CH..., even in rounds.

 

[gm89uk]

19 percent! Never seen that ragingly high CH in a round.

 

[OoohShiny]

19 percent! Never seen that ragingly high CH in a round.

We need pics!

 

[HappyNewLife]

I care more about diameter than weight. My 2.937ct ACA is 9.3mm on the smallest side, which puts it at the 3ct "size". Saved a bunch of money for the same size diamond? FINE WITH ME!

 

[gm89uk]

I've always thought that true spread should be mm/carat (diameter / carat ^(-3)

Correction diameter / carat^(1/3).

@HappyNewLife that's a great spread! So if it was a 1 carat that would measure 6.52mm to put it into context.

 

[oldminer]

This weight to size ratio is relative to other selection tools and data. If you have a 2.50 that spreads like a 2.65 and you love that added visual size, then it might make sense to consider the added size as part of your way of "valuing" that stone, but it won't excite everyone. However, if you have a equally well spread 2.85 that visually appears to be a 3.02 stone, then that might inspire more interest among a larger number of shoppers. There is a value issue on top of the visual size issue when crossing over a threshold carat weight. There is importance to visual size to weight ratios, but it is not exactly the same for every weight of diamond. How much this ratio is worth to each potential buyer is not always the same. It depends on the diamond in question.

To decide on 1 diamond, one must gather several facts together and make an informed decision based on the overall feelings that the numerous facts present. When you have more than 3 variables, selection based on additional variables becomes a task that human's don't do well with. Sometimes such data may be useful and sometimes it should be disregarded. What to appreciate and what to ignore should be in the hands of consumers for them to decide the level of importance. Experts are full of opinions, but the individual tastes of consumers are not all alike. Consumers need facts more than they need opinions.

I often think of the many, many consumers who have bought 2 ct total weight solitaire earrings with badly cut round diamonds that have the spread of 0.70 - 0.80 diamonds. They could have done far better getting two diamonds which were well cut and a total weight of 1.40 to 1.60, but there was no way for them to appreciate or understand how the meager spread of those lumpy 1.00 carat diamonds was not a benefit based on their weight.

The proposed strategy could be very helpful for shoppers to understand the nature of the diamonds they are shopping for. I do see this as a more useful tool for those buying non-excellent cut diamonds. At the top level of light return and appearance, a couple percent may mean nothing, but when cut is already compromised, the faults often add up to small visual size to weight, and it is rarely clearly revealed. Use of this ratio would open up an easily understood fact on those diamonds to almost every careful buyer.

 

[diamondseeker2006]

As usual, we are talking rounds only so I’ll just add my humble 2c’s...
I agree with Karl, especially on the bold part.
3D optical effects are as important as diameter size, if not more..., in fancy cuts they are even more substantial but that is for another thread.

In any case, I personally would much rather prefer a 6.30mm with a 17-19% CH than a 6.42mm 14% CH..., even in rounds.

Now that’s true! My AVR comes to mind with a 19+% crown height with a small table. It loses maybe .1mm in diameter as compared to a modern ideal cut, but I would not trade that high crown and small table for more diameter. I think that stone has perfect dimensions! (Cut by Yoram!) But I am assuming Garry is talking strictly modern rounds, and those usually dont have high crowns. The 6.3’s often are deeper or have thicker girdles.

 

[Texas Leaguer]

I think Garry's proposal needs to be seen in the context of the HCA tool. As an additional metric I think it definitely adds value. Particularly (as I understand it) his algorithm will attempt to factor in both spread AND edge brightness.

Anything that tends to re-educate the consumer away from a focus on weight is helpful, considering how they have been mislead for more than a century to believe that weight was something to aspire to, independent of performance and beauty.

The front end of the HCA tool is fairly simple and user friendly. Although I agree with @oldminer in principle that diagnostic tools like this should be as objective as possible, one of the things consumers seem to like about HCA is the light performance results are expressed in relatable descriptions. So I can see this new spread factor being expressed similarly. I do share @diamondseeker2006 concern that calling properly spread stones BIG (along with stones slightly on the smaller side) might be misleading. Maybe it should be called 'Ample' or something. (undersized, slightly undersize, ample, slightly oversize, oversize)

As an additional thought, maybe the descriptions should be updated to a more modern common parlance like: Failing, Weak, Bigly, and Yuge

 

[diamondseeker2006]

 

[oldminer]

big, big, big, big, big
Above is a system which is totally unbiased. Joking, of course.

Pick a mid point range of "most promising desirability" and call it "Excellent". Make equal terms on the + or - side of Excellent for over or under sizing.
Poor- Fair- Good- Very good-Excellent- Very good- Good- Fair- Poor

The exact range of Excellent and the other terms can be up to those qualified, such as Garry or by a group of Pricescope expert vendors. Those who have studied this relationship and features of cut performance over many years. Not everyone will agree it is perfect, but that doesn't mean that it is wrong or dishonest. People rarely agree with inventive ideas, but that's exactly how progress comes about.

 

[Garry H (Cut Nut)]

Hi Garry,

I've always thought that true spread should be mm/carat (diameter / carat ^(-3)) which I discussed here to standardise every carat to 1carat

https://www.pricescope.com/community/threads/diamond-depth-are-we-too-strict.239598/

Then you can compare any carat weight and diameter against the 6.3mm or whatever margin you choose. If you have easy access to analyse lots of diamonds on HCA, you could define big as mean + 1sd.

My gut instinct is 6.3 is a bit lenient to be "big" but I haven't analysed this over thousands of diamonds.
https://www.jamesallen.com/loose-di...color-vs2-clarity-true-hearts-cut-sku-2536114

This 62.7% depth 1 carat managed to get 6.42mm.

How about an Bigger, Big, Average, Small, Smaller?
Average from -1sd to 1sd, big small > or less than 1 sd and biggest, smallest 2sd.

Would this replace spread on HCA?

Great - Average GM. Like it! BTW you do need a base number in that formula. I use 1.00ct = 6.44mm. OctoNus and AGS use different numbers. Mine is based on a slightly thicker girdle.

 

[Garry H (Cut Nut)]

I think Garry's proposal needs to be seen in the context of the HCA tool. As an additional metric I think it definitely adds value. Particularly (as I understand it) his algorithm will attempt to factor in both spread AND edge brightness.
Thanks Bryan, very much part of the plan - the leakage adds a small % in a few cases, but can reduce the apparent size by approaching 10% or more.
Anything that tends to re-educate the consumer away from a focus on weight is helpful, considering how they have been mislead for more than a century to believe that weight was something to aspire to, independent of performance and beauty.

The front end of the HCA tool is fairly simple and user friendly. Although I agree with @oldminer in principle that diagnostic tools like this should be as objective as possible, one of the things consumers seem to like about HCA is the light performance results are expressed in relatable descriptions. So I can see this new spread factor being expressed similarly. I do share @diamondseeker2006 concern that calling properly spread stones BIG (along with stones slightly on the smaller side) might be misleading. Maybe it should be called 'Ample' or something. (undersized, slightly undersize, ample, slightly oversize, oversize)

As an additional thought, maybe the descriptions should be updated to a more modern common parlance like: Failing, Weak, Bigly, and Yuge

Dave and All, I am opposed to listing numbers, at least until a patent is granted.

 

[Paul-Antwerp]

Hi Garry,

As far as consumer-motivation goes, I agree that the magic weight of 1Ct will be valued higher by most consumers than a 0.95 Ct.

But I disagree that it is related to naming rights or a girl's (a guy's, for that matter) frickle behavior.

I see it far more related to an entire industry 'educating' for approximately a century, if not longer, that the value of a diamond is determined by the 4 C's. One of these C's is Carat Weight, and consumers are simply reacting to what 'the industry' is teaching them, incorrectly.

Personally, I do not believe that consumers (before 'incorrect' education) care about the small differences in carat weight, which they will find hard to discern. Far more important for them is sparkle and other factors of light performance. For sure, if they are sporting a truly sparkly stone, they will get far more positive comments, and far more 'naming or bragging rights' will be attached to that.

Live long,

I created a separate thread, related to the red comment above, where I explain my position on the 4 Cs in more detail. https://www.pricescope.com/community/threads/what-makes-a-diamond-valuable-the-4-cs-really.243729/

Live long,

 

[bmfang]

I like this proposed new feature. Most of the mall jewellers I’ve come across here is Australia usually caveat their ungraded 1ct stones as being anywhere between 0.92 to 1.02ct (though I suspect a lot of those 1ct stones are in fact closer to the 0.92ct size in order to pad up retail profit margins).

 

[Garry H (Cut Nut)]

I like this proposed new feature. Most of the mall jewellers I’ve come across here is Australia usually caveat their ungraded 1ct stones as being anywhere between 0.92 to 1.02ct (though I suspect a lot of those 1ct stones are in fact closer to the 0.92ct size in order to pad up retail profit margins).

Ungraded colourless or near colourless diamonds should almost not exist today. If they do, then there will always be serious things wrong with them.
Usually the girdle thickness is similar to the crown height.
Most reputable firms can source those goods for you for very low prices.
Hard to imagine firms can offer under 1ct diamonds as 1ct. The ACCC would have them for breakfast!

 

[Garry H (Cut Nut)]

gm89uk I am going with your suggestion of 'average' to make 5 grades for apparent size. Bigger, Big, Average, Small and Smaller (or maybe Very Small?). It works well with actually being around 'average' (sadly).
I hope that in some small way we can move (nudge?) the market to provide better value and better bigger looking diamonds.
The chart shows just how bad things are.

The cause of the problem.
Thanks for the idea

 

[Serg]

gm89uk I am going with your suggestion of 'average' to make 5 grades for apparent size. Bigger, Big, Average, Small and Smaller (or maybe Very Small?). It works well with actually being around 'average' (sadly).
I hope that in some small way we can move (nudge?) the market to provide better value and better bigger looking diamonds.
The chart shows just how bad things are.

The cause of the problem.
Thanks for the idea

Garry,

Things are not very bad. The chart does not proof that we have many poorly 1ct diamonds .
If a cutter rejects to cut 0.95ct-0.99ct RBC , it does not mean that he will cut poor 1.00ct RBC from same rough. yes, instead 0.98-0.99ct RBC he usually cuts 1.00ct RBC
But he also cuts 1.00ct Cushion, Oval,..when he can cut just 0.95-0.98ct RBC.

it is the reason why we see much more 1.00ct diamonds than 0.95-0.99ct

 

[Garry H (Cut Nut)]

Garry,

Things are not very bad. The chart does not proof that we have many poorly 1ct diamonds .
If a cutter rejects to cut 0.95ct-0.99ct RBC , it does not mean that he will cut poor 1.00ct RBC from same rough. yes, instead 0.98-0.99ct RBC he usually cuts 1.00ct RBC
But he also cuts 1.00ct Cushion, Oval,..when he can cut just 0.95-0.98ct RBC.

it is the reason why we see much more 1.00ct diamonds than 0.95-0.99ct

It would be nice if it were that simple Sergey.

However the numbers of diamonds with smaller millimetre spreads that are below optimal 0.95ct that weigh 1.00ct plus is horrific.
And I am using 1.00ct = 6.44mm as a benchmark. Smaller than AGS and DiamCalc.