Right table and depth percentages?

[jrich]

What are the ideal percentages for a round? Will be selecting a stone from James Allen and I know there are specific numbers the percentages should fall in. I have seen different numbers in different places so wanted to check with the experts here. Also, there seems to be a "premium" cut with JA, that falls between excellent and very good. I know I don't want to go down to very good, but can anyone comment on the premium cuts? Thank you!

 

[ruby59]

A diamond expert will see this shortly, but here is a cheat sheet written by one of the experts, Gypsy, which will help you with what parameters you should stay within to get a high quality cut diamond.

As quoted by Gypsy:


depth - 60 - 62% - although my personal preference is to allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate!

Also, configurations depend on each other. A little give here can still work with a little take there.

With that said, here''s a "Cliff''s Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35).

 

[Rockdiamond]

HI All!

Actually, Gypsy is a prosumer ( a knowledgeable consumer) - however there are also tradespeople posting here on PS.
I feel that the cheat sheet posted above leaves some of the nicest stones there are on the "cutting room floor" as it were.
Is it possible for you to see some GIA or AGSL graded diamonds jrich?
There's a variety of really well cut proportions that are considered extremely well cut- yet produce notably different types of sparkle and brilliance.

 

[Dancing Fire]

HI All!

Actually, Gypsy is a prosumer ( a knowledgeable consumer) - however there are also tradespeople posting here on PS.
I feel that the cheat sheet posted above leaves some of the nicest stones there are on the "cutting room floor" as it were.
Is it possible for you to see some GIA or AGSL graded diamonds jrich?
There's a variety of really well cut proportions that are considered extremely well cut- yet produce notably different types of sparkle and brilliance.

a 60/60?...

 

[Gypsy]

A diamond expert will see this shortly, but here is a cheat sheet written by one of the experts, Gypsy, which will help you with what parameters you should stay within to get a high quality cut diamond.

As quoted by Gypsy:


depth - 60 - 62% - although my personal preference is to allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate!

Also, configurations depend on each other. A little give here can still work with a little take there.

With that said, here''s a "Cliff''s Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35).

THANK YOU ruby HONEY!
It's not written by ME though. It is written my John Pollard A very respected TRADE MEMBER who worked at Whiteflash and now works at a boutique diamond cutting house called Infinity, and Lorelei another Prosumer on these boards.

I just copy and paste it where relevant. LOL.

 

[yssie]

A diamond expert will see this shortly, but here is a cheat sheet written by one of the experts, Gypsy, which will help you with what parameters you should stay within to get a high quality cut diamond.

As quoted by Gypsy:


depth - 60 - 62% - although my personal preference is to allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate!

Also, configurations depend on each other. A little give here can still work with a little take there.

With that said, here''s a "Cliff''s Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35).

I am not getting in the middle of a debate.. this is just MY opinion, as another consumer: there are exactly two good uses for that cheat sheet: to give to your insurance adjuster in the case of a claim, or to shoot yourself in the foot with if you're searching for a stone yourself. Consider that AGS uses scanners w/ stated error of +/- 0.1degree and all of a sudden all this nitpicking over 41 vs 41.1 starts to look a bit - well, overly enthusiastic...

There really are a variety of proportions that can make for a beautiful stone - and, conversely, a stone with "cherry" numbers by that cheat sheet could be a total doozy, we'd need a lot more info than just the numbers on the report to be able to say anything about nuances in light return with certainty. Try playing with the HCA https://www.pricescope.com/tools/hca and GIA's facetware tool https://www.gia.edu/facetware/ , find some trends, go out to a jewellery store and see how those trends play out IRL, find out what *you* like to see

 

[Gypsy]

Yssie, I agree with you to an extent. I would add a third use: to give to any BM jeweler who is sourcing stones for you or to take with you when shopping in person. Any of the cheat sheets we give are fallible-- ultimately the choice comes down to an actual determination of individual stone's stats and characteristics. But when used like the HCA to weed out stones that are completely unsuitable, I think it's a good tool. As a rejection TOOL it's pretty good. But just that... a single tool.

The "best" and most fool proof 'cheat sheet" is to tell people to stick to stones with AGS certificates that get a 0 for light return and at least excellent on polish and symmetry. But that 'cheat sheet' would raise a TON of objection with people who (validly) would say that there are a TON of great GIA stones that are being ignored.

All tools have their pluses and minuses. I think this one has more pluses than minus, and I understand that you don't agree. I think both viewpoints are valid.

My question is... what tool or set of information would you offer to someone who is looking for a guideline, if not this one?

 

[yssie]

Yssie, I agree with you to an extent. I would add a third use: to give to any BM jeweler who is sourcing stones for you or to take with you when shopping in person. Any of the cheat sheets we give are fallible-- ultimately the choice comes down to an actual determination of individual stone's stats and characteristics. But when used like the HCA to weed out stones that are completely unsuitable, I think it's a good tool. As a rejection TOOL it's pretty good. But just that... a single tool.

The "best" and most fool proof 'cheat sheet" is to tell people to stick to stones with AGS certificates that get a 0 for light return and at least excellent on polish and symmetry. But that 'cheat sheet' would raise a TON of objection with people who (validly) would say that there are a TON of great GIA stones that are being ignored.

All tools have their pluses and minuses. I think this one has more pluses than minus, and I understand that you don't agree. I think both viewpoints are valid.

My question is... what tool or set of information would you offer to someone who is looking for a guideline, if not this one?

We do disagree, and I think we agree that OP generally benefits more from dissenting opinions than parrots

I agree that the HCA is an excellent tool to start with. It's far less restrictive than the cheat sheet, and the "anything under 2" disclaimer avoids the natural newbie tendency to find the "perfect" crown and "perfect table" and "perfect" everything else in some misguided effort to get a stone right in the middle of the venn diagram...

It's not perfect, but it's a really good starting point. The next step is to find trends in the numbers, and take note of them. Find out what sorts of combinations yield what sorts of HCA outputs, plug them into facetware and see what GIA would say... at this point you still don't have any actually applicable knowledge, but you've built the bridges. Then make an appointment at a jewellery store that sells stones with reports and look at stones with various proportions. Find out what *your* eyes like to see, and see how the numbers on the stones you like best across a variety of lighting types correlate to HCA trends.

Then come back online, and now you have a much better idea of what you're searching for, and more importantly why you're searching for it. And we can help with all the other details.

This is, of course, time-consuming (though perhaps no more than reading threads and threads and threads to try and make sense of it all online!)... but I think most people who come to PS for help do want to do it *right*, so... there's my cheat sheet

 

[Gypsy]

We disagree. And I think we agree that OP benefits more from dissenting opinions than parrots.

I agree with the above and always have. I don't know why you would think otherwise. I was trying to open a dialog with you, since you do know more about rounds than I do, to see if perhaps I SHOULDN'T post the cheat sheet anymore or to be more restrictive when I do. That's all I was trying to do Yssie. Thanks for your opinion.

 

[yssie]

We disagree. And I think we agree that OP benefits more from dissenting opinions than parrots.

I agree with the above and always have. I don't know why you would think otherwise. I was trying to open a dialog with you, since you do know more about rounds than I do, to see if perhaps I SHOULDN'T post the cheat sheet anymore or to be more restrictive when I do. That's all I was trying to do Yssie. Thanks for your opinion.

Hey, no offense taken - I'm not trying to shut this down. Yeah, I'd like to see the cheat sheet gone, but I'm one side of the debate - and there wouldn't be a point to PS if there wasn't anyone on the other! Don't change your posting Gypsy, RT needs your opinion, and RT needs this sort of discussion.

I reread and saw my post came off as kinda terse so I edited to make it read more like what I mean!

 

[Gypsy]

The next step is to find trends in the numbers, and take note of them. Find out what sorts of combinations yield what sorts of HCA outputs, plug them into facetware and see what GIA would say... at this point you still don't have any actually applicable knowledge, but you've built the bridges. Then make an appointment at a jewellery store that sells stones with reports and look at stones with various proportions. Find out what *your* eyes like to see, and see how the numbers on the stones you like best across a variety of lighting types correlate to HCA trends.

Yssie I've been on the boards for 6 years and *I* couldn't do this. I really couldn't. I have noticed that you are very good with mathematics. To someone like me, the angles and correlations are like Greek-- without having someone TUTOR me and walk me through the morass of numbers I couldn't come up with anything other than gibberish (as in me being reduced to it) from looking at the numbers and the stones.

I do agree that your approach is a great one. But I don't think it is something everyone can do, or has the time to do or has the inclination to do. And I don't think it's a 'cheat sheet' ... more like a plan of action to get really good results.

BUT what you said about the HCA being the best starting point is great so I will modify my approach to these posts to stressing the use of the HCA.


Thank you for your comments above. I think I will add in disclaimers to the cheat sheet about it's limited application and about the HCA.

 

[yssie]

I'm sorry Gypsy I really didn't mean to make it personal. ::HUG::
Now quit being so formal, would you?

or has the time to do or has the inclination to do

Y'know.. I still have such a hard time believing this might ever be the case. And of course it might be - call it the curse of the lab rat! When I first found PS I was on those numbers like I was starving... now I find myself backing off more and more, though. There is a real and definite disconnect between what the stone is *doing* and what I see, and what you see may well not match what I see, and of course you and I might want to see different things, and... trying to nicely box all of that in and ship it out as a universal fix is, I'm starting to believe, simply impossible!

Where's Dreamer to disagree with both of us? Actually I'm thinking her trademark approach is perfect in cases like the above - find a GIA EX or AGS, plug it into HCA and if it scores well (I'd put the cap at 3 personally) Go Forth and Be Fruitful!

 

[Gypsy]

I'm sorry Gypsy I really didn't mean to make it personal. ::HUG::
Now quit being so formal, would you?

or has the time to do or has the inclination to do

Y'know.. I still have such a hard time believing this might ever be the case. And of course it might be - call it the curse of the lab rat! When I first found PS I was on those numbers like I was starving... now I find myself backing off more and more, though. There is a real and definite disconnect between what the stone is *doing* and what I see, and what you see may well not match what I see, and of course you and I might want to see different things, and... trying to nicely box all of that in and ship it out as a universal fix is, I'm starting to believe, simply impossible!

Where's Dreamer to disagree with both of us? Actually I'm thinking her trademark approach is perfect in cases like the above - find a GIA EX or AGS, plug it into HCA and if it scores well (I'd put the cap at 3 personally) Go Forth and Be Fruitful!

You didn't necessarily make it too personal. I think I've just got thin skin right now... probably not the best time to be on the boards. ((HUGS)) back. Don't worry about it. I've just got some crap IRL I'm dealing with that's making take criticism a little seriously.

I have to agree that Dreamer's approach is a good one. It's ACTUALLY what I would do IN REAL LIFE. IF I wasn't buying a super ideal precision cut from Infinity or BGD (which would be my personal preferred vendors for this type of stone, but we all have our preferences) and wanted a deal on something with great performance-- I'd call up one of the vendors here known for having lower prices (so ID jewelry, Eternity Diamonds, ERD, Perry Chen) and just tell them I wanted a GIA stone that scores well on the HCA and an ASET or IS of the same (if they can provide it), or an ASG 0 light performance stone.

But on the other hand, I am comfortable with PS vendors and much prefer them to MOST real life vendors and I know that some of the RT stone hunters aren't.

 

[Rockdiamond]

For what it's worth- I don't suggest tossing the cheat sheet- rather putting it in context.
We can agree that the list will produce a fairly consistent result- however there are other results which are arguably as good using PS logic- that is to say table/depth combos that fall in the "sweet spot"- meeting both both GIA Triple EX and AGS 0 cut grade.

SO- the cheat sheet is an opinion.
If it's John Pollard's opinion, it's a well respected opinion I agree- but framing it as factual rather than subjective is where I see a problem.
After all, shoppers might encounter seller that have differing preferences. They themselves may have different preferences- if they look at things unbiased by a cheat sheet...OK, maybe I do think it should be trashed....

Why not take the "crosshairs" stones- those that meet both GIA and EX cut grade as a "cheat sheet"
Just a suggestion.

 

[Garry H (Cut Nut)]

You can compare GIA and AGS grading based on table sizes and crown and pavilion angles with the tables from links in the upper left of this page, and compare the master stones that we are building with various proportions and with lots of tools and data from here http://www.octonus.com/oct/mss/table.phtml

David it would help us all save time if you had a good 1/2 hour study here too.

 

[diamondseeker2006]

Yssie, I agree with you to an extent. I would add a third use: to give to any BM jeweler who is sourcing stones for you or to take with you when shopping in person. Any of the cheat sheets we give are fallible-- ultimately the choice comes down to an actual determination of individual stone's stats and characteristics. But when used like the HCA to weed out stones that are completely unsuitable, I think it's a good tool. As a rejection TOOL it's pretty good. But just that... a single tool.

The "best" and most fool proof 'cheat sheet" is to tell people to stick to stones with AGS certificates that get a 0 for light return and at least excellent on polish and symmetry. But that 'cheat sheet' would raise a TON of objection with people who (validly) would say that there are a TON of great GIA stones that are being ignored.

All tools have their pluses and minuses. I think this one has more pluses than minus, and I understand that you don't agree. I think both viewpoints are valid.

My question is... what tool or set of information would you offer to someone who is looking for a guideline, if not this one?

We do disagree, and I think we agree that OP generally benefits more from dissenting opinions than parrots

I agree that the HCA is an excellent tool to start with. It's far less restrictive than the cheat sheet, and the "anything under 2" disclaimer avoids the natural newbie tendency to find the "perfect" crown and "perfect table" and "perfect" everything else in some misguided effort to get a stone right in the middle of the venn diagram...

It's not perfect, but it's a really good starting point. The next step is to find trends in the numbers, and take note of them. Find out what sorts of combinations yield what sorts of HCA outputs, plug them into facetware and see what GIA would say... at this point you still don't have any actually applicable knowledge, but you've built the bridges. Then make an appointment at a jewellery store that sells stones with reports and look at stones with various proportions. Find out what *your* eyes like to see, and see how the numbers on the stones you like best across a variety of lighting types correlate to HCA trends.

Then come back online, and now you have a much better idea of what you're searching for, and more importantly why you're searching for it. And we can help with all the other details.

This is, of course, time-consuming (though perhaps no more than reading threads and threads and threads to try and make sense of it all online!)... but I think most people who come to PS for help do want to do it *right*, so... there's my cheat sheet

Yssie, I am also going to say this was absolutely impossible for me. Even the higher end stores I went to had no selection of excellent/dial cut stones that I could analyze (like you can really tell how anything looks in that lighting anyway!). Your suggestion is great, but I tend to think that short of walking in Good Old Gold, we'd have a slim opportunity of doing this. I am just imagining now going into Tiffany with my scopes, asking them to see all the lab reports, and asking that huge guard next to the front door if he could move a bit so I can compare stones in natural light!

Yssie, the cheat sheet was for people who couldn't access really good stones and wanted to buy from vendors sight unseen. I am pretty sure I was one of the first who started posting the basic table, crown, pav., depth info and later other people expanded on it. I found out what ACA proportion ranges were so that people could have those parameters if they shop elsewhere. I will say that I do now not obsess over numbers on AGS0 stones. If someone comes here and posts an ideal cut, I tell them that light performance has already been analyzed and I don't worry about the numbers. But with GIA stones, it is extremely helpful to have something to begin to narrow down the better stones in the excellent range. Those numbers generally work well in the HCA.

It would be super if I could see stones with all the possible combinations! Maybe I would find some that I like as well or even better than the ones on the cheat sheet. Maybe Rockdiamond will just send me some to look at so I won't have to be so limited in my preferences! I'd love to take you diamond shopping with me, too! But since those two things are unlikely to occur, I'll pretty much have no choice but to stick to the cheat sheet or else stick with GOG, WF, and BG who have preselected outstanding stones for buyers like me.

 

[ruby59]

I am the one who answered the OP and provided the cheat sheet. After being on Pricescope for many years, I try and help in a very limited capacity if the tradespeople and prosumers are not around as I hate seeing people with questions that have no response to them. I read similar questions posted to the right and respond accordingly. I always state a diamond expert will be there shortly, and here is some information to get you started.

Gypsy, the reason I quoted you as the writer, is because you added some personal additions to the cheat sheet. I know Lorelei has not posted in ages. So I usually defer to you, Yssie, Dreamer, and Stone Cold.

Bottom line - Has the cheat sheet become obsolete? Or should it still be recommended to those who state they have a limited knowledge of diamonds, and that it should be used as a guideline with disclaimers that it is ONLY a starting point?

 

[Rockdiamond]

HI Ruby
From my perspective this cheat sheet started out obsolete
For sure, a stone cut that way will be well cut.
My main problem is that the sheet excludes a lot of great stones - including proportion sets I would find more attractive- others will too
So if we use them as a starting point we've already eliminated some amazing GIA EX stones

There's a lot of well meaning folks here- some have had great experience with a given vendor- and may adopt the same principles as their favorite- or course thats their right
But the danger is that a prolific consumer poster who may seeem like an expert may have been strongly influenced by the opinion of a vendor they trust which can in turn create a one sided type of advice being given

 

[diamondseeker2006]

But RD, for someone who is trying to find a great diamond in the midst of a haystack of mediocre to poor stones, they have to have some parameters to go by. If you want to provide a list with alternate measurements for great stones, please do so. But to the novice, almost all diamonds look pretty good unless they are highly included and cloudy. So it is just imperative for them to have some guidance when threads asking for help are posted.

 

[Rockdiamond]

Great point DS
How do you feel about the " crosshairs" idea?

This way it won't be my preference or yours or Garry's etc
Both labs include a wider viriety of proportion sets than the cheat sheet so both larger table and smaller tables are represented.

 

[Dancing Fire]

Great point DS
How do you feel about the " crosshairs" idea?

This way it won't be my preference or yours or Garry's etc
Both labs include a wider viriety of proportion sets than the cheat sheet so both larger table and smaller tables are represented.

my preference have always been for stones that are inside AGS 0 cut and GIA Ex cut charts.

 

[diamondseeker2006]

I am definitely open to adding the broader range of AGS0 specs so that people can search within the GIA Excellents to get the better stones, if that is what you meant, RD. But I am not sure that is what you mean. Because you don't like the zone in the HCA that shows the AGS0/GIA Ex overlap, right? I understand there are different opinions on preference, but we still have to have a fairly simple way for a newcomer who wants to buy an e-ring in the next week how to identify a stone that will be a great one.

 

[Rockdiamond]

I am definitely open to adding the broader range of AGS0 specs so that people can search within the GIA Excellents to get the better stones, if that is what you meant, RD. But I am not sure that is what you mean. Because you don't like the zone in the HCA that shows the AGS0/GIA Ex overlap, right? I understand there are different opinions on preference, but we still have to have a fairly simple way for a newcomer who wants to buy an e-ring in the next week how to identify a stone that will be a great one.

Yes DS!
That's precisely what I'm suggesting.
If a stone can achieve GIA EX, as well as AGSL 0, it's "in the cross-hairs"

Let me also clarify the fact that I'm sure stones selected from the cheat sheet would be very nice- and that I love such stones. The reason I don't like the sheet is the stones it excludes- although I prefer a larger table, I can surely see the beauty in a well cut 57% tabled stone

 

[Rockdiamond]

You can compare GIA and AGS grading based on table sizes and crown and pavilion angles with the tables from links in the upper left of this page, and compare the master stones that we are building with various proportions and with lots of tools and data from here http://www.octonus.com/oct/mss/table.phtml

David it would help us all save time if you had a good 1/2 hour study here too.

Hi Garry!
I don't see the relevance of the page you linked to this discussion whatsoever.
I'm not big on trying to impart what a diamond looks like with computer generated graphics- even knowing diamonds as well I do, the CG images don;t really conjure up diamonds in reality. Plus, if we judge a diamond when it's stationary, as compared to adding movement, we're not getting the full picture- not nearly.
There is no "right" table/ depth.
I do agree that a collection of images and videos showing how different combos create differing appearances would be a boon to consumers.
All due respect, but I didn't get that from your page.