Crown Angles Greater than 40 degrees
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diamondsbylauren
Brilliant_Rock
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Headlight! Buy a stone with a 61% table????? How could you????
I have seen AWESOME stones with 61% tables.
Here's one thing about all this conversation that concerns me. Say someone owns a diamond that scores badly on the HCA- and say they love said diamond. The possibilty exists that a person reading this might conclude that they have a "bad" diamond. Even if they do have a badly cut stone- if they loved it before I feel that there's something wrong in changing their opinion.
Then you have folks like headlight- headlight's stone pretty much shows that just because HCA says a diamond is not well cut, that in no way means that it's not a desirable or pretty diamond.
Of course this is a dinasaur's opinion, pay no heed.
I have seen AWESOME stones with 61% tables.
Here's one thing about all this conversation that concerns me. Say someone owns a diamond that scores badly on the HCA- and say they love said diamond. The possibilty exists that a person reading this might conclude that they have a "bad" diamond. Even if they do have a badly cut stone- if they loved it before I feel that there's something wrong in changing their opinion.
Then you have folks like headlight- headlight's stone pretty much shows that just because HCA says a diamond is not well cut, that in no way means that it's not a desirable or pretty diamond.
Of course this is a dinasaur's opinion, pay no heed.
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Once a diamond is given it becomes a symbol of love and your relationship. This is far more important than how it performs.
If a young couple working part time and educating themselves buy an engagement ring with a 0.10ct center diamond - is it less important or special than another couples 1ct ring?
HCA is not a judgemental tool, it is a selection rejection aid to narrow down the field of possabilities.
It is also a tool for diamond cutters who wish to maximize the yeild of a rough diamond and at the same time create a beuatiful diamond.
Now that AGS and soon GIA are going to move to HCA type cut grading, we will waste a lot less diamond in the cutting process too.
If a young couple working part time and educating themselves buy an engagement ring with a 0.10ct center diamond - is it less important or special than another couples 1ct ring?
HCA is not a judgemental tool, it is a selection rejection aid to narrow down the field of possabilities.
It is also a tool for diamond cutters who wish to maximize the yeild of a rough diamond and at the same time create a beuatiful diamond.
Now that AGS and soon GIA are going to move to HCA type cut grading, we will waste a lot less diamond in the cutting process too.
diamondsbylauren
Brilliant_Rock
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Garry- Have you let Kerry and Bush know about the HCA?- in additon to saving all the rough diamonds, it might be able to create world peace!
Let's be accurate here- Neither GIA nor AGS recognizes or uses the HCA.
It's true that GIA is going to be offering a "Cut Grade" in the near future- but nowhere does it say that GIA is using HCA as a model.
With all due respect Garry- this thread proves the point that folks feel like there may be something wrong with their diamond if it scores low on the HCA. It also points out that the HCA score and the beauty of a diamond might not neccesarily be related. Are telling headlight she should have rejected her diamond?
Signed,
David- the beautiful diamond crusader.
Let's be accurate here- Neither GIA nor AGS recognizes or uses the HCA.
It's true that GIA is going to be offering a "Cut Grade" in the near future- but nowhere does it say that GIA is using HCA as a model.
With all due respect Garry- this thread proves the point that folks feel like there may be something wrong with their diamond if it scores low on the HCA. It also points out that the HCA score and the beauty of a diamond might not neccesarily be related. Are telling headlight she should have rejected her diamond?
Signed,
David- the beautiful diamond crusader.
moremoremore
Ideal_Rock
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Actually, if headlight doesn't mind and if I'm not mistaken...I believe that she selected her own stone despite its HCA...she likes to upgrade!
headlight
Ideal_Rock
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On 10/15/2004 5:40:20 PM moremoremore wrote:
Actually, if headlight doesn't mind and if I'm not mistaken...I believe that she selected her own stone despite its HCA...she likes to upgrade!
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Yes, MMM, I certainly do like those upgrades (short attention span
As you can see, I became a member in 11/2003, six months after acquiring the stone (5/5/03) -- Timing IS everything, isn't it?!!!
And while I am sure that Garry did not develop the HCA to make people "reject" the diamonds they already own but rather to have a tool for which to make the best selection possible on future purchases, what David said is true as I did go through a very conflicted period where I seriously doubted my judgement in my purchase of this stone and was very unsatisfied as a result of learning about angles and percentages and what to look for, as David has participated in a number of threads in which I discussed this uncertainty.
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David while AGS nor GIA are going to endorse HCA, HCA is my best interpretation of the nature, physics and beauty of the best and worst round diamonds.
So if AGS and GIA release similar systems to HCA, then it might be reasonable to expect that the advice provided by HCA would have been proven to be very useful to those consumers and members of the trade who have used the service and avioded buying say AGS >41 degree pavilion >35 degree crown angle diamonds. I think it would be fair to predict that my development has saved many many thousands of such purcheses and the resultant fall in value that those buyers would suffer as their diamonds drop from current AGS 0 to new AGS 3-4.
The chart shows the new AGS candidates for table size 55%.
I have constructed a similar chart for GIA based on the little data they released at Basel show this year and again at HK fair. It too indicates a strong resemblance to HCA.
In addition I have inside connections with many people from gem labs. They frequently read these forums but of course may not post.
Trust me David - you can continue to eat dinasuar food, or start to change your diet now before the fooder goes rancid.
So if AGS and GIA release similar systems to HCA, then it might be reasonable to expect that the advice provided by HCA would have been proven to be very useful to those consumers and members of the trade who have used the service and avioded buying say AGS >41 degree pavilion >35 degree crown angle diamonds. I think it would be fair to predict that my development has saved many many thousands of such purcheses and the resultant fall in value that those buyers would suffer as their diamonds drop from current AGS 0 to new AGS 3-4.
The chart shows the new AGS candidates for table size 55%.
I have constructed a similar chart for GIA based on the little data they released at Basel show this year and again at HK fair. It too indicates a strong resemblance to HCA.
In addition I have inside connections with many people from gem labs. They frequently read these forums but of course may not post.
Trust me David - you can continue to eat dinasuar food, or start to change your diet now before the fooder goes rancid.
diamondsbylauren
Brilliant_Rock
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Garry-
I repeat- I do not see this as personal- if it makes you feel better, I'll say I thought about this overnight, and decided that you're 100% correct, and I am 100% wrong. OK?
Seriously- if you can make sense of the graph you posted, I take my hat off to you. What does it mean? And why should anyone need to learn how to interpret something like this to buy polished diamonds?
GIA's new cut grade will rely heavily on visual examination, not graphs.
Fact: GIA has chosen NOT to use machines like the "Colorimeter"
For those who have never heard of this machine: You put the diamond inside press a button, and ka-poof! You have a graph which needs no learing curve to read. It's the color scale- and it plots the distance between H,and I and shows you where your H color stone sits within the grade of H.
GIA is well aware of this machine, yet they do not use it.
What I take this to mean is this: It's got to pass a visual test as an H to be an H. GIA feels that humans have to call it an H.
What will happen if GIA's cut grade gives the top cut grade to a stone your invention says is doggy doo?
ON many occasions I have met with the owners and general managers of both EGL USA, and IGI here in NY to discuss grades. We speak to GIA on a daily basis because we submit quite a few stones- and we discuss grades with the lab. Does that give me connections? NO
I say NO- because I would stress, with the greatest emphasis, that knowing these people has no impact whatsoever with the operations of those labs- or the grades they might issue. I'll be the first to say that I feel EGL USA, IGI and of course GIA strive to maintain the highest standards and issue grades as they see them.
Has GIA consulted you for assitance in the new cut grade?
Garry- Have you skiied Vail?
I repeat- I do not see this as personal- if it makes you feel better, I'll say I thought about this overnight, and decided that you're 100% correct, and I am 100% wrong. OK?
Seriously- if you can make sense of the graph you posted, I take my hat off to you. What does it mean? And why should anyone need to learn how to interpret something like this to buy polished diamonds?
GIA's new cut grade will rely heavily on visual examination, not graphs.
Fact: GIA has chosen NOT to use machines like the "Colorimeter"
For those who have never heard of this machine: You put the diamond inside press a button, and ka-poof! You have a graph which needs no learing curve to read. It's the color scale- and it plots the distance between H,and I and shows you where your H color stone sits within the grade of H.
GIA is well aware of this machine, yet they do not use it.
What I take this to mean is this: It's got to pass a visual test as an H to be an H. GIA feels that humans have to call it an H.
What will happen if GIA's cut grade gives the top cut grade to a stone your invention says is doggy doo?
ON many occasions I have met with the owners and general managers of both EGL USA, and IGI here in NY to discuss grades. We speak to GIA on a daily basis because we submit quite a few stones- and we discuss grades with the lab. Does that give me connections? NO
I say NO- because I would stress, with the greatest emphasis, that knowing these people has no impact whatsoever with the operations of those labs- or the grades they might issue. I'll be the first to say that I feel EGL USA, IGI and of course GIA strive to maintain the highest standards and issue grades as they see them.
Has GIA consulted you for assitance in the new cut grade?
Garry- Have you skiied Vail?
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David I have not skiied Vail, but firends say it is probably better than Aspen, but they perfer the old town of Aspen to the new vail.
The attached chart is what GIA have released so far. They will be telling all (or more anyway) in the Fall issue.
Actually I do discuss these things with lots of people in higher places than the book in counter, although not GIA as much because we are competitors (we have an arrangement being worked out with HRD and through them we hope with others).
So for what it is worth, my little crusade is probably one you should learn about.
BTW those HCA type charts are going to become a regular way of visualizing cut grades. GIA will use them and probably calculators like HCA too.
The attached chart is what GIA have released so far. They will be telling all (or more anyway) in the Fall issue.
Actually I do discuss these things with lots of people in higher places than the book in counter, although not GIA as much because we are competitors (we have an arrangement being worked out with HRD and through them we hope with others).
So for what it is worth, my little crusade is probably one you should learn about.
BTW those HCA type charts are going to become a regular way of visualizing cut grades. GIA will use them and probably calculators like HCA too.
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He Ha He Elmo
It is bad for my lungs and throat though
Lyn I asked this on the (very interesting!) thread that you started, but I think it kinda got "lost" in the shuffle!
I'm not quite sure what to make of that AGS graph -- what with it skipping every other number. ???! So how do I figure out one like mine, (34.8/40.9)? Will it still be AGSO 0?
Many, many thanks!
Lynn>>>
Lyn you can see that your stone is right on the border line. Both GIA and AGS seem to be using terms like "candidates" for certain grades based on the proportions. In AGS case - the finish (sym and polish will be combined to one term with less importance than now), the durability and the spread needs to be all in the right zone. After that, minor facets could ugrade or downgarde a stone.
But if your stone has a great Ideal-scope image then I am pretty sure you would get the new AGS grade.
It is bad for my lungs and throat though
Lyn I asked this on the (very interesting!) thread that you started, but I think it kinda got "lost" in the shuffle!
I'm not quite sure what to make of that AGS graph -- what with it skipping every other number. ???! So how do I figure out one like mine, (34.8/40.9)? Will it still be AGSO 0?
Many, many thanks!
Lynn>>>
Lyn you can see that your stone is right on the border line. Both GIA and AGS seem to be using terms like "candidates" for certain grades based on the proportions. In AGS case - the finish (sym and polish will be combined to one term with less importance than now), the durability and the spread needs to be all in the right zone. After that, minor facets could ugrade or downgarde a stone.
But if your stone has a great Ideal-scope image then I am pretty sure you would get the new AGS grade.
moremoremore
Ideal_Rock
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I just noticed this. How does that GIA cert for thar DBL cushion say crown angles greater than 40 degrees. I saw that on another cusion sold by DBL also? I don't understand...GIA does that?
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MMM they only do it as a warning - for instance on rounds they note crown angles under 30 or over 36 etc.
The warning is in the comments field.
I do not know if 40 is the first or only warning with cushions - it probably is - but at 40 degree crown angle the spread is going to suffer, even if the brilliance does not.
The warning is in the comments field.
I do not know if 40 is the first or only warning with cushions - it probably is - but at 40 degree crown angle the spread is going to suffer, even if the brilliance does not.
moremoremore
Ideal_Rock
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I almost think you're joking LOL! I had no idea GIA does that. I thought that GIA never commented on cut...Interesting! Thanks for the info. Do you think that could lead to problems with setting stones like that...I'm not looking, but just wondering
diamondsbylauren
Brilliant_Rock
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MMM
When a round diamond has "crown angles greater than 35degrees" the GIA adds that comment, as Garry said. A cushion shaped diamond gets the comment at crown angles over 40 degrees.
AS far as setting- a lot of the beautiful double prong antique prong designs are perfect for a stone with a more full crown.
In a colorless cushion, the heavy crown gives the real antique look.
In fancy color cushions, it allows the cutter more room inside the stone with which to focus the color within the stone.
Look at it this way- say a cutter is offered a nice rough which yeilded the 2 and a half carat cushion, or the 4.09 Light yellow.
When these people cut the diamonds they must make the decisions which will result in the cut of the finished diamond.
Were the cutters "wrong" to choose the stones with crown angles greater than 40degrees?
It's easy to say "the diamond should be cut this way" or that- yet, the people who cut these diamonds understand the rarity, and difficulty in obtaining such rough diamonds.
It's in their best interest to cut desirable stones- and of course they must also consider the yeild.
This 2.51 Cushion has crown angles greater than 40- which gives the small table and a very antique look which is IMO timeless.
Garry-are you saying that the tye dye graph comes from GIA?
When a round diamond has "crown angles greater than 35degrees" the GIA adds that comment, as Garry said. A cushion shaped diamond gets the comment at crown angles over 40 degrees.
AS far as setting- a lot of the beautiful double prong antique prong designs are perfect for a stone with a more full crown.
In a colorless cushion, the heavy crown gives the real antique look.
In fancy color cushions, it allows the cutter more room inside the stone with which to focus the color within the stone.
Look at it this way- say a cutter is offered a nice rough which yeilded the 2 and a half carat cushion, or the 4.09 Light yellow.
When these people cut the diamonds they must make the decisions which will result in the cut of the finished diamond.
Were the cutters "wrong" to choose the stones with crown angles greater than 40degrees?
It's easy to say "the diamond should be cut this way" or that- yet, the people who cut these diamonds understand the rarity, and difficulty in obtaining such rough diamonds.
It's in their best interest to cut desirable stones- and of course they must also consider the yeild.
This 2.51 Cushion has crown angles greater than 40- which gives the small table and a very antique look which is IMO timeless.
Garry-are you saying that the tye dye graph comes from GIA?
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High crown angles did not cause any problems here - they are all just under 41 degrees
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