Blue Nile Reviews – Signature Ideal Princess Cut Diamonds

Blue Nile* advertises its Signature Ideal Princess-Cut Diamonds with a number of lofty claims. Below is the headline statement from their Education page at http://www.bluenile.com/signature-ideal-princess-diamonds:

In order to test the claim that these are in fact “the first and only princess-cut diamonds with ideal standards”, along with several other questionable representations made about the diamonds in this category, we purchased five Blue Nile Signature Ideal Princess cuts and conducted scientific light performance analysis using AGS Performance Grading Software. We also captured reflector images of the diamonds using ASET and Ideal Scope to reveal their light handling characteristics.

Blue Nile markets this line of princess cut diamonds with a GIA report and a secondary report from GCAL. It should be noted that while the GIA report does include separate grades for polish and symmetry, it does not provide an overall cut grade for princess cuts. Interestingly, none of the diamonds tested had GIA’s top grade (Excellent) for both polish and symmetry. Each diamond reviewed had only Very Good on one or both aspects. This is apparently in contradiction to Blue Nile’s own claim about the diamonds in the category:

The grades and measurements were found to be consistent with the less rigorous standards set forth in the specifications for the Signature Ideal Princess-Cut as stated in this simple table:

The Analysis The first step in our analysis was to perform a Sarin scan of each diamond that accurately measures every facet dimension and angle. This information was then fed into the AGS Performance Grading Software that mathematically calculates the behavior of 40,000 separate light rays applied to the 3D model of the diamond. Among other attributes analyzed, the output provides grades of the diamond’s performance on the key characteristics of brightness, dispersion (fire), contrast, and leakage. The AGS light performance grading system is the most technically advanced and scientifically rigorous grading system in existence. You can find the foundational peer reviewed study published in the journal Optical Engineering.

AGSL grades on a 0-10 scale, where 0 is defined as Ideal, indicating zero deductions. Deductions for light performance deficits are added together cumulatively to determine the final LP grade. For example, if brightness, and dispersion had deductions of 0.500, and contrast and leakage were 0, the LP grade would be 1. That would equate to AGS 1 or Excellent – the grade just below Ideal.

We analyzed the Blue Nile “Signature Ideal” princess cuts using the PGS software and none of them achieved AGS0 Ideal. The results were one AGS 3, one AGS 2, and three AGS 1’s. (In the following section you will find the grading data showing specific deductions, cumulative total deductions, and resulting grade.)

Next, we captured actual light performance images with ASET and IdealScope reflectors. These images provide visual evidence of light return, light leakage and contrast. Below are the images of the five sample Blue Nile Signature Ideal Princess cuts along with the PGS light performance data and the basic parameters from the GIA report. The ASET images on left shows light return in red (brightest) and green (less bright) with leakage in black (contrast shows in blue but is difficult to distinguish from the black in these images). The IdealScope images on right shows light return in red and leakage in white. Black is a reflection of the camera lens and contributes to contrast. (Positive contrast is necessary for scintillation, so too little can result in a deduction as well as too much).

The accompanying report from GCAL is intended to verify the GIA report. Blue Nile states that it “ensures that each diamond meets the quality requirements of the Blue Nile Signature Collection”. Apparently that means verification that the diamond falls within the ranges that appear in the Signature Princess-Cut table:

There is also a cut grade included in the GCAL report, along with Polish and Physical Symmetry with simply state “Blue Nile Signature Ideal”. There is also a grade for “Optical Brilliance” which indicates “Excellent” for all the diamonds in the sample. The explanation for the methodology of this test which appears on the report is the following:

The scale indicates that Excellent is defined as at least 88% light return. We noted that the optical brilliance image does not appear to show as much leakage as we can see in both the ASET and IdealScope around the table (as in the example of GIA1156230427 below), so it is unclear exactly how the GCAL image is processed. What is clear is that it is a more forgiving standard than AGS Ideal.

Based upon the samples tested, we believe that the marketing claims put forward by Blue Nile regarding their Signature Ideal Princess are largely unfounded. The use of the term Ideal to characterize these diamonds is highly misleading. Not a single one of the samples would qualify for the grade of AGS Ideal, the diamond industry’s top standard for overall cut quality, and in fact none of the diamonds even received the top grades for the cutting aspects indicated on the GIA reports which accompany them. Furthermore, light performance imaging reveals a wide range of visual light performance characteristics among the samples, with each of them showing obvious performance deficits. All samples studied had issues with brightness and light leakage. In our opinion the claim that Blue Nile Signature Ideal Princess cuts are manufactured to exacting standards is undermined by both the significant variances and the deficits revealed by our testing.

We also tested the following claim on the Blue Nile Signature Princess cut education page and found that claim to be untrue.

http://www.bluenile.com/signature-ideal-princess-diamonds

A random sample of 25 diamonds from the industry’s largest wholesale trading network included not a single diamond that had a depth as great as 88%.

Blue Nile makes a point to emphasize the importance of crown height and claims that Signature Princess has “exacting proportions”. However, the stated range in their standards goes from 8.5 to 13.5%, a variation of more than 50%. This is hardly a strict standard nor can such a range be considered “exacting”.

The claim that the BN standard for crown height “almost doubles the industry standard”, would imply that the industry standard is from 4.25% to 6.75%. Our survey of the network also reveals this claim to be unfounded.

With regard to Blue Nile’s claim that their “Signature Ideal Princess Cut-Diamonds are “the first and only princess-cut diamonds with ideal standards”, this is clearly not true. AGSL certified Ideal princess cut diamonds are most definitely available in the market. Below are examples of Princess cuts which come with AGS 0 platinum certificates.

Although we found the diamonds acquired from the BN Signature Ideal Princess category to be better than average commercial quality, we believe that the unsubstantiated claims of superior quality and performance are inaccurate and misleading, and likely to cause consumer confusion over key attributes of the diamonds in this category.