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    Choosing James Allen princess cut diamond for Viachi engagement ring

    Hi Todd, the ring is perfect. I proposed last night and all went wonderfully. She absolutely LOVES the diamond and the ring. Thank you SO much for all of your help. You (and your website) allowed me to make an educated decision about this monumental purchase. I greatly appreciate all of your assistance. Without you (and your website) I feel that I would have made a multi-thousand dollar purchase without understanding the intricacies of the product. Thank you. — Derek T.

    It can be very difficult to find princess cut diamonds that exhibit exceptional light return and sparkle, this tutorial will teach you what to look for…

    Princess Cut Diamonds 101: Basic Facts

    Unlike round brilliant ideal cut diamonds, which are symmetrical in shape and feature a standard facet structure of 57 facets with a bottom point known as the culet; princess cut diamonds can be square or rectangular in shape and generally feature anywhere between 24 to 48 facets or more, depending on the preferences of the diamond cutter, and what adjustments the cutter had to make while cutting the diamond due to the nature of the diamond rough that the diamond is being cut from.

    Generally speaking, princess cut diamonds are cut from diamond rough which is not symmetrical in shape, it is a different diamond rough than is used to produce round brilliant cut diamonds, and it costs less… which is why princess cut diamonds tend to cost less per carat than round brilliant cut diamonds of the same carat weight, color, and clarity.

    Because princess cut diamonds tend to be cut much deeper than round brilliant cut diamonds, they tend to face-up smaller in terms of outside diameter than a round diamond will for the same relative carat weight, e.g. an ideal cut round brilliant cut diamond cut weighing 1.00 carats, which is cut to proportions that are within my preferred range, is likely to have an outside diameter of approximately 6.50 millimeters, while a princess cut diamond of the same carat weight is likely to have an average diameter of only 5.6 mm.

    Best “Ideal Proportions” for Princess Cut Diamonds:

    Unlike with round brilliant ideal cut diamonds, it can be extremely difficult to buy princess cut diamonds “by the numbers” because the measurements for the crown and pavilion sections can be influenced by the facet structure of the diamond, and the number of chevron facets polished on to the lower half of the diamond can change the entire look of the diamond as well as the sparkle factor.

    However basic guidelines for what the best and ideal proportions are for selecting princess cut diamonds which are likely to provide higher levels of light return are as follows:

    Proportions chart princess cut diamonds courtesy of David Atlas, Accredited Gem Appraisers

    I usually find that princess cut diamonds exhibiting higher levels of light return fall into the range of AGA Class 1A Ideal Cut, AGA Class 1B Premium Cut, and AGA Class 2A International Fine Trade Cut; therefore when searching for princess cut diamonds like the one that I helped Derek find, I limit the total depth of the diamond between 64 – 75% and the table diameter between 59 – 74% and look for the tightest combination of proportions possible.

    In this particular instance, during our search for princess cut diamonds on James Allen, we didn’t find any suitable options with a total depth within the range of 64 – 75% but did find an option just beyond that range at 75.1% which is certainly “close enough” for all intents and purposes. If you want to save yourself a bunch of time searching for princess cut diamonds on James Allen, simply click on the link provided above, because I’ve encoded the search parameters into the link, and then you can simply adjust the range of carat weight, color, and clarity, to suit your preferences.

    AGS Ideal vs GIA Excellent Princess Cut Diamonds:

    Best proportions tutorial princess cut diamonds, James Allen, AGS 104067101006I definitely prefer princess cut diamonds that have been graded by the American Gem Society Laboratory (AGSL) because of the insight provided into the overall cut quality of the diamond by the Angular Spectrum Evaluation Technology (ASET) that the AGSL uses to measure diamonds for brightness. The ASET image provided on the diamond grading report pictured to the left, indicates that the 1.53 cart, H-color, VS-1 clarity, princess cut diamond from James Allen that Derek purchased is extremely bright, based upon the high volume of red, which is the color used to represent the highest level of brightness; the color green is used to represent the second brightest light which enters the diamond; and I also look to confirm that the pattern of light that is reflecting through the diamond is being evenly distributed by the facet structure, which it clearly is.


    The biggest challenge that I have with princess cut diamonds that have been graded as GIA Excellent by the Gemological Institute of America (GIA) Gem Trade Laboratory (GIA-GTL) is that the GIA Laboratory does not provide crown height, crown angle, pavilion depth, or pavilion angle measurements for the fancy shape diamonds that they grade… thus it is practically impossible to determine where the proportions of a GIA graded princess cut diamond fall on the proportions chart provided by David Atlas above, without asking the vendor to provide you with a computerized proportions analysis by Sarin | OGI | or Helium scans, which most of them are reluctant to provide.

    How Chevron Facets on Princess Cut Diamonds influence Sparkle:

    Chevron facets are the chevron shaped facets that are polished on the lower half or pavilion section of a princess cut diamond, they extend outward from the primary pavilion main facets that appear in the center of the pavilion and look like a large ‘X’ as indicated on the graphic below which was provided to me by my friend Paul Slegers of Crafted by Infinity.

    Effects of 2 - 3 - 4 chevron facets princess cut diamond configurations

    In my experience, princess cut diamonds that feature two and three chevron facets on the underside of the diamond, and which are cut to ideal proportions, tend to be brighter in appearance and exhibit flashes of light / sparkle which are broader in size, and bolder and brighter than the sparkle exhibited by princess cut diamonds with four chevron facet configurations.

    In addition, I tend to think that princess cut diamonds polished with four chevron configurations tend to look like “crushed ice” and it is not a look which I am personally fond of; however this is not to say that they are not pretty diamonds, they’re simply not the kind of diamond that I am personally drawn to… one of the reasons why princess cut diamonds are cut with a variety of facet structures is because it provides people with options in terms of what appeals to their personal sense of beauty; the other reason is because it allows the cutters to adjust for variations in the diamond rough, but that is another subject entirely…

    So if you count the chevron facets that appear on the 1.53 cart, H-color, VS-1 clarity, princess cut diamond from James Allen that Derek purchased, you’ll see that it features two chevron facets, and obviously Derek thinks that it is gorgeous!

    Advice for finding the best princess cut diamond:

    As stated previously, it can be a bit tricky to shop for princess cut diamonds online, because it is not as simple as limiting your search to a specific range of total depth, table diameter, crown angle, pavilion angle, and girdle thickness… it is not possible to buy princess cut diamonds by the numbers, as it is possible to do with rounds, especially if you have access to the reflector scope images that we use to judge optical symmetry, such as ASET Scopes, Ideal Scopes, and Hearts and Arrows viewers (not applicable for princess cut diamonds).

    So you might want to take advantage of my free Diamond Concierge Service if you’d like help finding an exceptional princess cut diamond. Just drop me a note and let me know the range of carat weight, color, clarity, and price that you are working with, and whether you think you prefer a princess cut diamond that exhibits broad, bright flashes of light / sparkle (2 – 3 chevron facets) or prefer smaller pin-fire type sparkle and that crushed ice look, so that I can be most effective when searching for princess cut diamonds on your behalf.

    If you’ve already conducted your own search for princess cut diamonds on James Allen, or another vendor, please include links to the diamonds which are of interest to you, I’ll be happy to look over the details for you and provide you with an opinion.

    About the AuthorTodd Gray

    Todd Gray is a professional diamond buyer with 30+ years of trade experience. He loves to teach people how to buy diamonds that exhibit incredible light performance! In addition to writing for Nice Ice, Todd "ghost writes" blogs and educational content for other diamond sites. When Todd isn't chained to a desk, or consulting for the trade, he enjoys Freediving! (that's like scuba diving, but without air tanks)

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