AGS & GIA Ideal Cut Diamonds & Wholesale Diamond Price Guides

When a diamond comes out of the ground it looks like a shiny pebble or piece of quartz. In fact, it is so unimpressive that it would be amazing if you actually recognized it as a diamond. The first diamond discovered in South Africa (not the world) was found in 1866 when a young shepherd named Klonkie hurled it at one of his friends, Erasmus Jacobs, who pocketed it and gave it to his sister to play with. Quite some time later, a visitor to the Jacobs home commented that the shiny pebble might be a diamond. Eventually, it was confirmed as being a diamond weighing 21.25 carats and was cut into what is now the 10.73 carat oval brilliant Eureka Diamond.

Precision cutting is necessary to release the beauty of a diamond. The brilliance, fire, and scintillation that make diamonds so desirable is the result of how skillfully a diamond is cut. With this in mind, it's time for you to realize that Cut is the most important, and least understood, factor of the 4C's.

Lay people often confuse a diamond's SHAPE with its CUT, this is most likely due to the industry's synonymous use of the terms "cut" and "shape" to describe a diamonds shape (outline), i.e. marquise cut, round brilliant cut, or pear shape. In reality when we refer to the "cut" or "make" of a diamond, we are really referring to a compilation of three factors. its PROPORTIONS in terms of degrees and percentages... the quality of it's POLISH or finish... and the SYMMETRY of it's facets... These three factors result in the "Overall Cut Grade" of the diamond.

If you remember only one thing from this site, remember this...

98% of a diamond's brilliance is controlled by the quality of it's cut, not it's clarity, color, or size... but rather, it's proportions, polish, and the symmetry of it's facets. The other 2% is in your head and generally represents your mistaking a brighter color such as D-E-F for brilliance. None of the other factors, color, clarity, or carat weight, have more of a dramatic effect on a diamonds beauty that it's cut. Subtle and minute dimensional differences of half a millimeter or less can determine whether a diamond will be full of life or dull and listless.

With that in mind, we'd like to introduce you to the concept of "Ideal Cut" diamonds. That is, diamonds cut within a specific range of "ideal proportions" that consistently deliver maximum brilliance. Just as you can reap the benefits of a great haircut, or look like a dork for six weeks, diamonds look their best when they have been cut to precise proportions. Diamonds cut to these precise proportions are called "Ideal Cuts" and are certainly worth looking for, especially since you don't have to look any further than our Private Reserve

Now it seems that Ali Baba & The 40 Thieves have stolen a box of micrometers and would lead you to believe that every round brilliant cut diamond is an "Ideal Cut". Can you say camel dung?

Now, we're not saying that everybody in the jewelry industry is a thief, or a member of Ali Baba's gang, but even the tooth fairy knows that a diamond is not "Ideal Cut" simply because it has a 60/60 Table and Depth ratio. Or simply because it would be "ideal" for the jeweler to sell you a diamond from his inventory. We're not kidding about the unfortunate reality of this game... In fact, here's an ideal example courtesy of a netite who recently consulted us regarding an "Ideal Cut" he thought he'd found at a price too good to be true. It was...

Here's what Stephen had to say to us in his last email:

"The stone I found which the jeweler (name removed to protect the not-so-innocent and to keep us from being sued) said was all AGS Ideal (even though it was not certified) was sent out to AGS in mid-December for a Diamond Quality Document as you suggested (I insisted on this)... Well thank God I did because the stone came back AGS-6 Cut "a-la-sucko"! I was very disappointed... Luckily AGS turned me on to another jeweler in my area who sells the "Hearts & Arrows" diamonds... They helped me find a beautiful diamond (0.85 ct. H, SI-2, Hearts & Arrows). The thing is unbelievable. I have never seen anything so gorgeous, it lights up a dark room. I gave her the diamond last week and she said Yes!!! Thanks again & happy new year!!! (Stephen B.; December 30, 1997).

Lucky for us, we don't have to take Ali Baba's word for it when he says that a diamond is "Ideal Cut"... The American Gem Society (AGS) has developed a precise definition for the proportions of a true "Ideal Cut" diamond... Now in case you've never heard of AGS before, they are the "sister company" of the Gemological Institute of America (GIA) and the first major gemological laboratory to create and use a system for grading the proportions of a diamond.

The AGS Cut Scale has eleven categories used to describe the proportions of a round brilliant cut diamond, the highest rating is AGS Ideal-0 and the lowest is AGS-10 Poor. The overall cut grade of the diamond is determined by taking all of the factors (3) which comprise of (1) the PROPORTIONS combined with the (2) POLISH and (3) SYMMETRY ratings for the diamond... A diamond that receives the AGS Ideal rating for all three categories of the AGS Cut Grade (proportions, polish, and symmetry) is formerly known as "AGS IDEAL-0" but is commonly referred to within the diamond industry as "AGS-000" or "triple zero ideal cut"... Regardless of the name, one of these Super Ideal Cut Diamonds will make the hairs on a gnats posterior stand up and quiver... That's a politically correct, California colloquialism for those of you who can't handle the word "ass"... If you're ready to find one, visit our Private Reserve of Nice Ice

To properly determine the proportions rating of a diamond, it is mandatory that you know the Table Diameter (%); the Crown Angle (in degrees) which is NOT the same as the crown height; the Pavilion Depth (%); the Girdle Thickness (%); and the Culet Size... For your convenience the broad spectrum parameters for the AGS Ideal Cut proportions rating for round brilliant cut diamonds is as follows:

Table Diameter:	52.4 - 57.5%
Crown Angle:	33.7 - 35.8° degrees
Pavilion Angle:	40.15 - 41.20 degrees
Girdle Thickness:	Thin, Medium, Slightly Thick
Culet Size:	None, Pointed, Very Small, Small, or Medium

Note that the Total Depth % of the diamond is not taken into account. This is because it is the Crown & Pavilion angles that control most of the brilliance and thus the Total Depth is not as important a factor. Just the same, we prefer that the total depth of a round brilliant cut diamond be somewhere between 59.0% and 61.8% with the ceiling being around 62.5% in our opinion. Although it is not uncommon to find AGS Ideal Cut diamonds with total depths as deep as 63.5% we recommend that you avoid them like the plague because they are simply too deep!

Proportion information for round brilliant cut diamonds is provided on AGS Diamond Quality Documents and GIA Diamond Grading Reports in the form of a diamond graphic which is a scale model of the diamond represented by the diamond grading report as based upon the actual measurements of the diamond. Although the crown and pavilion angle measurements are provided on the lab reports, we do not rely on these measurements to judge the cut quality of the diamond because they represent the average measurements for the crown and pavilion angles. It is important to review a Sarin or OGI computerized proportions analysis which divulges what the spread of the high and low measurements are for each section that comprises the average measurement indicated on the lab report. Think about it. If the average crown angle measurement indicated on the lab report is 34.5 degrees and the lowest crown angle measurement is 34.3 degrees and the highest is 34.8 degrees, that is great! But if the low measurement is 33.5 degrees and the high measurement is 35.5 degrees, that is less than desirable (okay, it sucks!) but the average measurement indicated on the graph provided on the lab report would still be 34.5 degrees.

The next trick that Ali Baba and his den of thieves likes to rely on is the infamous tale of Marcel Tolkowsky. A physicist and member of a Belgian diamond cutting family, who in 1919 published Diamond Design, the first analysis of diamond proportions. His work was based on [what were then] modern theories of light behavior and his opinion of what proportions resulted in the best possible balance of brilliance and dispersion of light.

Ali Baba likes to say things like "This diamond has Tolkowsky proportions, but I didn't want to increase the price of the diamond by having it certified"... This is usually bunk, if all of the proportions for the diamond met Tolkowsky's parameters, he would have sent it in for certification...

Tolkowsky's calculations for the ideal angles and proportions for a round brilliant cut diamond are as follows:

Notice that Tolkowsky specified that the girdle edge of the diamond be "Knife Edge" or virtually non-existent... It's great in theory, however many a girdle edge has been chipped because it was extremely thin and could not withstand the pressure of being set... Interestingly enough, a knife edge girdle would result in a rating of AGS-10 Poor on the AGS Proportions Scale. Perhaps this is why we have yet to see a diamond that is cut to Marcel Tolkowsky's true standards. Instead what we see are a lot of diamonds cut within "tolerance of Tolkowsky's standards" or "Tolkowsky Range".

Using Sarin DiaPort computerized proportions analysis, we have evaluated a variety of "Tolkowsky Cut" diamonds and have determined that the proportions of the diamond can range from AGS Ideal to AGS-2 Very Good. Therefore, we recommend you only consider a "Tolkowsky Cut" diamond when you have all of the information required to determine the actual proportions of the diamond. The parameters of the AGS Ideal Cut rating are far more accurate than what Tolkowsky created on his chalkboard seventy years ago...

Our Private Reserve of Nice Ice is filled with round brilliant ideal cut diamonds with proportions that can be verified as falling within the range of the zero ideal cut. We are a "House of Ideal" and only sell round brilliant ideal cut diamonds... If you're looking for something really spectacular and want to exceed the bragging rights of a "Tolkowsky Cut" then we recommend you select one of our Hearts & Arrows puppies and present the diamond to your fiancée unmounted with a little ditty about how each of the eight hearts represents a special way you feel about her.

Although we only sell true Ideal Cut Diamonds, we thought that you might find the parameters for the AGS-1 Excellent through AGS-3 Good range of interest... The average light return for a diamond with AGS Ideal Polish, Symmetry and Proportions is around 96%... The average light return for a diamond with AGS-4 Good Polish, Symmetry and Proportions is somewhere around 70% which might help you to understand why we only sell ideal cuts.

AGS-1 Excellent Proportions

Table Width - %	51.4 - 52.3% -or- 57.6 - 59.5%
Crown Angle - Degrees	32.7°^- 33.6° -or- 35.9° - 36.3°
Pavilion Depth - %	43.9 - 44.3%
Girdle Thickness	Very Thin
Culet Size	Slightly Large

AGS-2 Very Good Proportions

Table Width - %	59.6 - 61.5%
Crown Angle - Degrees	32.2°^- 32.6° -or- 36.4° - 36.8°
Pavilion Depth - %	41.7 - 42.1% -or- 44.4 - 44.8%
Girdle Thickness	Very Thin to Slightly Thick
Culet Size	Slightly Large or Smaller

AGS-3 Good Proportions

Table Width - %	50.4 - 51.3% -or- 61.6 - 63.5%
Crown Angle - Degrees	31.7°^- 32.1° -or- 36.9° - 37.3°
Pavilion Depth - %	41.7 - 42.1% -or- 44.4 - 44.8%
Girdle Thickness	Thick
Culet Size	Large

Unless you're comparing diamonds graded by a laboratory, it might not be easy for you to determine the actual proportions or cut rating of a diamond. Most diamond dealers and jewelry store owners actually don't calculate the proportions of the diamonds that they buy and sell. They select them based on how brilliant they look and price them accordingly. If a diamond looks dull and lifeless, an experienced diamond grader knows that it's poorly cut. The diamond will sell easily to an inexperienced buyer who only considers size, clarity, and color when shopping for a diamond. A lot of companies on the net rely heavily on this fact, hence the abundance of on-line diamond search engines and long inventory lists of diamonds for sale. Ever notice how the crown angles and pavilion depth measurements are seldom listed for you to compare? Not to worry, this information is available to you in our Private Reserve because we want you to know what you are buying.

Evaluating A Diamond For Brilliance:

When evaluating a diamond for brilliance, you should look at it both with and without magnification. For best results, your light source should be diffused, such as a fluorescent or shaded lamp. Diffused natural daylight is one of the best sources for grading diamonds for brilliance. Do not use a bare light bulb or spotlight because while this type of lighting can accentuate a diamonds sparkle, it might also create dark shadows in the stone. Beware of jewelry store lighting which usually consists of halogen MR-16 bulbs or daylight bulbs that are designed to deceive by pumping high watt halogen streams into promotional goods to make them look like the crown jewels.

Well-cut, properly proportioned diamonds will be brilliant throughout the stone and will refract rainbow like colors, often even in a dimly lit room. Poorly cut diamonds will refract only white light, or appear dull and lifeless and often have dark or washed-out areas that allow you to see through the bottom of the stone. A diamond that has been cut too deep will often have a dark center called a nailhead. Diamonds that have been cut too shallow will often display a white circle around the table (top center flat facet) edge which is commonly referred to as a fisheye.

Here's a quick tip for you Type-A Engineer Types [like my dad] As you embark upon your quest for the perfect diamond, take a moment to realize that these little guys aren't stamped out on a production line… They're cut by hand out of material provided by nature… There are no hard and fast rules… There are no constants… No absolutes. A diamond is not going to be brilliant because it meets your spreadsheet analysis for the "perfect" combination of cut, color, clarity, and carat weight. The GIA grading system was created so diamond dealers and jewelry stores could communicate with each other over the telephone with some sort of consistency. The bottom line is that when it comes to selecting the "perfect" diamond, you're mind is going to have to be open to a wide range of possibilities. For instance, we've seen diamonds of comparable cut and clarity rated as I-J in color that look better than ones rated as F-G in color… Figure that one out! For your purposes, the GIA system should be used as a guideline and nothing more. Ultimately, you'll have to learn to trust your eyes and forget all about what the diamond is graded as and simply select a diamond that is brilliant. If you do that, you can't lose no matter what the diamond is rated as on paper.

Now, we know that last sentence was far too much for my dad's engineer brain to handle. In fact, it would probably produce convulsions due to synaptic overload… "Who can make such an important decision without complex mathematical calculations and grueling hours of intense analysis? Just use your eyes and pick the pretty one? Why it's simply not logical!" Relax Pops, take a chill pill… If you really need to evaluate everything, and consider all of the possibilities. We want you to enjoy the process! Heck, if it'll give you a thrill we'll even teach you how to calculate the proportions for yourself. God help the next jewelry store you walk into. They're going to absolutely LOVE IT when you show them how to calculate a diamonds proportions... NOT. Sadly, many jewelers don't know how to do that little trick themselves. So have fun and maybe you can teach them a few things! If you really want to have fun, visit our Diamond Grading Tools page and get your hands on a diamond grading loupe of your own.

Polish & Symmetry

Now in case you're thinking that you don't need to worry about all of this cut and proportions stuff because you've decided ONLY to consider diamonds Certified as having Very Good Polish & Symmetry then you have really missed the point of this entire page and we have some important news for you. Polish & Symmetry as it appears on most laboratory diamond grading reports and certificates has ABSOLUTELY NOTHING to do with the actual proportions of the diamond!

"POLISH" refers ONLY to the overall surface "Finish" of a diamond... The quality of a diamond's finish is determined in similar fashion to how you judged the quality of the last time you had your car "detailed". The more pristine the finish, the fewer "swirl" marks left by the polishing process, the higher the rating. As with your car, the better the polish, the brighter the diamond. While the average diamond buyer will be happy with a polish rating of "Good" we recommend a rating of at least AGS-2 Very Good and preferably AGS Ideal. By GIA standards this would be Very Good to Excellent. Of course, here in the office if the diamond doesn't have GIA Excellent or AGS Ideal polish and symmetry we shred the paper and reject the offering.

"SYMMETRY" refers ONLY to the consistency of facet shape and how well the points of each facet align with each other. The lack of proper pointing or facet shape, along with off center culets and tables, are common faults found when examining a diamond for symmetry.

The actual shape and proportions of a diamond are not considered when a diamond is graded for symmetry. A diamond can have extremely poor proportions and still be rated as "VERY GOOD" in Symmetry if it's facets are equal and the overall shape of the diamond is balanced. Likewise, a diamond can have AGS IDEAL CUT proportions and poor symmetry.

Some of the more common symmetry faults that diamond graders look for are: Round Brilliant Cut Diamonds that are "Out of round"; main & bezel facets that are out of alignment; facet points that do not meet; mis-alignment of the table and culet (table off-center); wavy, irregular, girdle pattern; table facet not parallel to the girdle plane; emerald shapes that are not rectangular; square shapes that are not square; etc.

Just as many people are perfectly happy with diamonds that fall within "Ideal Range" many people will be satisfied with a diamond that is rated as "GOOD" in Polish & Symmetry. Such a diamond will look perfectly fine to the untrained eye and will still be cost effective enabling you to purchase the largest, most brilliant diamond for your money. However, those of you seeking maximum brilliance should be looking for diamonds with symmetry ratings of AGS-2 Very Good to AGS Ideal. By GIA standards this would be Very Good to Excellent.

A diamond that receives the AGS Ideal rating for all three categories of the AGS Cut Grade (proportions, polish, and symmetry) or by the GIA Laboratory as having Excellent polish and symmetry with a zero Sarin analysis is truly a sight to see.

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Here's What We "Perfectionist Purists" Look For...

Now this next part is not for the weak of heart. It might ruin you as a diamond buyer forever. However, if you want to know what we'd buy if we were looking for the perfect engagement diamond here it is.

As previously stated, we consider the quality of a diamond's cut to be the most important of the 4C's due to the fact that the quality of a diamond's cut controls 98% of it's brilliance (i.e. "maximum reduction of light leakage"). If a diamond is cut properly it will almost always be brilliant regardless of it's clarity or color. Therefore, we recommend you look for a diamond with AGS Ideal Cut proportions and a Polish and Symmetry grade of either AGS Ideal or GIA Excellent.

Clarity? While you can certainly go cleaner if you've got the bucks, we recommend a clarity of SI-1 or VS-2 for most people. If the clarity is SI-1, then the diamond must be "eye clean" with no feathers or inclusions breaking the edge of the stone. The inclusions can be near the edge of the stone, but they can not break the edge of the stone. We will not sell an SI-1 clarity diamond if it is not eye clean to us during our evaluation. Which brings us to the point that not all SI-1 clarity diamonds are eye clean. SI-1 is a pretty broad clarity grade and there are some real bummers out there. We hand select every one of the diamonds that we sell in our Private Reserve to ensure you of the highest quality.

Color? This one's easy. Anywhere from D-Colorless to I-Near Colorless IF the diamond is AGS Ideal because the brilliance and dispersion of the stone will be the dominant factor especially when the diamond is set in a white gold or Platinum head.

Carat Weight? We don't consider this of importance at all... Buy the most brilliant, beautiful diamond that you can for your money. There will always be somebody with a bigger diamond, but few people have really beautiful diamonds because few jewelers share the importance of cut with their customers.

Cut	The Angle of the Dangle
Color	Spectral Bliss or Yuppie Yuck?
Clarity	Through The Looking Glass
Carat Weight	Does Size Matter?
How To Examine A Diamond	All Thumbs 101
Diamond Treatments	Plastic Surgery
Fluorescence	White Wash?
Detecting Simulants	To Be or Not To Be
Back To Start of Grading	Diamond Grading For Real People

May we help you find the diamond of your dreams?
Send us an email diamonds@niceice.com and tell us what you are looking for.
Or give us a call at 206.319.8152 or Toll Free 877.844.5443

AGS® is a registered trademark of the American Gem Society (702) 255-6500
GIA® is a registered trademark of the Gemological Institute of America (760) 603-4000

Cut - Proportions Control The Brilliance The Shape is NOT the Cut...