Ideal proportions?

[boomer]

I am considering purchasing a brilliant diamond of
1.08 carats. Can anyone help me out with some ideal proportions/measurements?

eg; measurements, table width, crown height, pavillion depth

by the way probably a dumb question but if a certificate says very good proportions and very good finish grade does this mean its safe to say I''ve got a pretty damn good cut?

 

[valeria101]

Forget the cert: it is very unlikely that the data available on it may allow to actualy evaluate the optical quality of the cut. The story is a long one, but if you take an hour or so to go through the "H&A" explanation here and the AGA cut charts, and, best of all, the cut tutorial on Good old Gold, this is probably the most you need to find out what exactly is there to measure about diamond cut and why. The "cut advisor" is a nice toy too...
Of course, you may or may not subscribe to such standards, but these are a good vaccine against any premium you may be asked to pay for unproven cut quality.

Hope this helps!

 

[pqcollectibles]

You can go to the Price Scope Tutorial "Home" page. In the left hand bar, toward the bottom of the page are links to Cut Charts. You can compare diamonds you are considering to the Cut Chart and determine it's Cut Class. After you determine Cut Class you can evaluate the asking price using the Price Stats link above. Price Stats gives average and low price averages being charged by Price Scope Vendors for comparable color/clarity/cut diamonds.

You still need more information than Table and Depth %'s, Crown and Pavillion %'s. You need Crown and Pavillion Angles as well. Once you have that information, you can use the Cut Adviser to help weed out poor performers. Ultimately tho, diamond selection comes down to your eye, what appeals to you, the diamond that speaks to you.

 

[mdx]

Hi Boomer

A real simple way if you dont want to get into the numbers and are able to inspect the stone is an Ideal scope. Check it out at https://www.pricescope.com/idealscope_indx.asp

Regards
Johan
Melbourne Diamond Exchange Ltd.

 

[Rhino]

Hi Boomer,




Merry Christmas! There are actually a number of various "sets" of proportions that will work within a round brilliant diamond. Those of us who do purchase diamonds for inventory can take one of a few routes in finding the most brilliant stones.




We can either

1. hunt down the needles in the haystack among traditional non ideal cuts or
   
2. purchase diamonds with known proportions (what we would refer to in the trade as triple ideal cuts) as long as we are familiar with the type of product coming from any given factory.

While option one does cost less for the individual stone (a non ideal will always be less expensive than an ideal or super ideal H&A) there is alot of cost *hunting* down those needles. Ie. less than 5% (that's 5 in 100) have proportions that will flatter the diamonds brilliance/fire but calling in (and paying shipping on) 100 stones to find 5 good ones is not very cost effective and in the end would cost me a heckuva lot more than paying a small premium for a stone that is coming from a factory with a known good track record. Having said that some of the particular proportions I look for specifically are rounds with crown angles between 34 - 34.7 with pavilion angles around 40.7-40.9 with tables between 53-57%. We would recommend other stones for purchase that differ from this but if the crown angles run steeper then the pavilion angles must compensate. After the basic proportions (which cover 17/57 facets) I then begin to look at minor facet cutting as this can also increase brilliance, fire & scintillation as well.

This will be an interesting factor to keep an eye on regarding GIA's upcoming cut charts because they also state that multiple sets of proportions will produce a very vibrant stone that do not fall within the tradition "ideal" standards. (ChrisK & Mara's diamond come to mind). When that does come out it'll be interesting to see what factories (on the wholesale end) start cutting diamonds to non-traditional ideal cut specs and how they would perform. There are a number of excellent people here who can help guide you into an awesome stone (NiceIce, WhiteFlash, etc.) and a bunch of consumers who regularly post here with nothing but your best interests in mind. Use this forum for all it's worth and you will be steered in the right direction. IMO it is the best forum on the net with regards to customer service and expert advice.

Kind regards,

 

[Mara]

----------------
On 12/25/2003 4:34:34 AM boomer wrote:





by the way probably a dumb question but if a certificate says very good proportions and very good finish grade does this mean its safe to say I've got a pretty damn good cut?

----------------

No it's definitely not safe to say you've got a good cut from just viewing polish and symm. All that means is that it was polished up nicely and the symmetry is good. Both have something to do with contributing to a well cut stone (more symmetry than polish actually) but don't mean a darn thing when viewed at on their own. To determine the cut of your stone you need table, depth, crown angle and pavilion angle at the very least. Girdle, fluor, culet all come in very handy as well. Is it an AGS graded stone? If so, post the #'s here and people can tell you more. If GIA graded it, they don't give you the angles, so you'd need to request a Sarin report from your jeweler in order to get those numbers and find out more.

Good luck!

 

[mdx]

Rhino Wrote

This will be an interesting factor to keep an eye on regarding GIA's upcoming cut charts because they also state that multiple sets of proportions will produce a very vibrant stone that do not fall within the tradition 'ideal' standards. (ChrisK & Mara's diamond come to mind). When that does come out it'll be interesting to see what factories (on the wholesale end) start cutting diamonds to non-traditional ideal cut specs and how they would perform. Kind regards,

----------------[/quote]


Hi Rhino
I think you are being a bit optimistic in the belief that thelarge cutters will start producing the non traditional Ideal Cuts. In our humble opinion the bulk of non traditional Pavilion/crown angle combinations are in the shallow cut stones, that is from 40.7 down to as low as 39.6. As we know although this area will produce larger looking stones the weight loss can be considerable if you don’t have flattish rough.
I believe the cutters are more likely to go the other way with pavilion angles above 41, The problem here is the number of possible viable crown angles falls off dramatically as the pavilion gets only slightly steeper.

Jonathan we are already seeing indications of large reputable cutters cheating on the pavilion facets while trying to maintain weight and achieving AGS 0 dimensional specs. Typically smaller lower girdle facets.

Johan
Melbourne Diamond Exchange Ltd.

 

[Giangi]

Hello Boomer,

since you're talking about very good finish grade and proportions, I assume you're talking about an HRD or EGL Antwerp cert. If I am right, then you can assume that you're getting at least a decent looking diamond. It may be gorgeous and ideal, but could have a large table, steep crown and deep pavilion as well. So no, you can't be 100% safe.
I strongly suggest you to post the data here and we'll be more than happy to help you with your selection.

 

[oldminer]

I look forward to seeing what the GIA will propose as "New version Ideal Cut rounds". Probably the stones that get cut in any volume will be deeper than standard for the very good reason of weight retention and relative rarity of shallow rough suitable to cut rounds from. One must keep in mind that to some people Ideal only means highly brilliant. This is only part of the total picture or definition of what is truly "Ideal"

An Ideal diamond is highly brilliant, but not so brilliant that scintillation or dispersion suffer tremendously. An ideal cut diamond is based on proper MODERATION of these important factors. Who would want a flat mirror-like diamond? There is more than simple light return.

An Ideal diamond is also fashioned to look its best. If it is overly thin it will be fragile. If it is overly deep, it will be smaller for a given weight and not look its size. Size does matter when it comes to diamonds.

So, regardless of what the future of IDEAL is, there are some factors that will not be changed. An Ideal diamond is a superb combination of cut, brilliancy, scintillation and dispersion. This is a very difficult set of paramters to objectively define, but we are getting there however slowly.

What the GIA offers will not be a cure-all, but any solid knowledge will be welcomed by those with open minds. In my experience, I believe we already have a great deal of the information we need to determine the very best cut diamonds of every normal shape. Getting dealers and cutters to agree on this is what has been difficult. Every cutter needs to be economically viable to survive. They all want to sell wht they cut and cannot all cut Ideal stones all the time. The market and the supply just don't allow it to happen. This is the most logical reason for years of resistance to defining the best of each of the regularly available fancy shapes. Economics.

The more the public clamors for finely crafted and highly brilliant diamonds, the more likely the economics will change to allow the supply to flow. The more consumers reject poorly cut and less brilliant stones, the sooner the market will react.

The tools consumers have today to help them select the best variety of diamonds has never been better. Even better information will be coming. Change for the better can't be all bad.

 

[mdx]

Hi Dave
What is going to be interesting is what format GIA will present there cut grading. The notion of max and min crown and pavilion angles cannot work, as this would either create a standard that eliminates some good performers or like AGS-0 will include a number of dogs. I would imagine it would need to be some sort of calculator like Diamcalc. Any ideas Dave

Johan
Melbourne Diamond Exchange Ltd

 

[blingslinger]

blingslinger say - if you like the bling then get blue nile signature round brillant ring