Costco Diamonds vs Blue Nile 2021 The Difference is Clear

Costco Diamonds vs Blue Nile Engagement Rings.

Sparkle Factor Results from Cut Quality - Blue Nile.

How do COSTCO Diamonds stack up against Blue Nile? We received this inquiry from a client who wants to know the difference between COSTCO and Blue Nile Diamonds:

"I'm looking at COSTCO Diamonds and Blue Nile. I like 1-1.5 carats and think we have a budget of 8K. But, we might be able to go up a little more than that depending on what Costco offers."

"I want a good diamond and like the pave petite round setting. I think that is the name. I am new to researching diamonds. Is this price range possible? Here are a few COSTCO Diamonds that I'm thinking about right now." -- Tina G.

Follow along and see whether Blue Nile or Costco diamonds are the best.

Tips For Buying Blue Nile and Costco Diamonds:

Costco Diamonds Review.

The COSTCO diamonds below are the ones that this client is considering. As with all of the diamonds that I review, we will consider them based on my selection criteria.

It's important to realize that there is only so much that you can tell about a diamond by the numbers. That is why I prefer evaluating loose and using reflector scopes to judge optical precision.

An ASET Scope reveals how well a diamond makes use of the available light in the room. It will also enable you to determine how evenly light reflects throughout the diamond and the degree of leakage.

In contrast, an ideal Scope only helps to identify light leakage. Unfortunately, neither Blue Nile nor Costco Diamonds provides these images routinely. In that case, it can feel like you're trying to buy diamonds in the dark.

Hearts & Arrows Scope:

Black by Brian Gavin Hearts and Arrows Diamonds.

Black by Brian Gavin Hearts and Arrows Diamonds.

In addition to ASET and Ideal Scope, we use a Hearts and Arrows Scope to verify optical precision. That is the consistency of facet shape, size, and alignment throughout the diamond. The combination of these factors will have a direct impact on the volume of light return and sparkle intensity.

Unfortunately, most box stores don't provide the reflector scope images necessary to judge light performance. Neither do most online retailers like Blue Nile. Consequently, I've never seen any H&A Scope images for Costco diamonds.

That makes it difficult to judge the degree of light leakage and their diamonds' light performance. On the other hand, diamond cutters like Brian Gavin provide those images for your peace of mind.

Costco Diamonds Review: GIA #5123030941

The characteristics of this diamond engagement from Costco are as follows:

  • IGI graded (ring description).
  •  1.13 carat, G-color, VVS-2 clarity, GIA Excellent cut diamond.
  • 950 Platinum rating and 1.55 carats combined total weight.

Let's begin by looking up this diamond using GIA Report Check. That way, we'll have all the relevant details, such as proportions and clarity characteristics. According to the GIA, the details of report #5123030941 for this Costco diamond are as follows:

  •  59.3% Total depth.
  • 59% Table diameter.
  • 32.5° Crown angle.
  • 40.8° Pavilion angle.
  • Thin to medium, faceted girdle.
  • Culet size: None.

How to Evaluate Costco Diamonds:

 Analyzing Diamond Proportions

If you're familiar with my selection criteria, then you know that this Costco diamond doesn't make the grade. In the first place, the crown angle of 32.5° is too shallow. Generally speaking, you want the crown angle to be between 34.3 to 35.0 degrees.

Comparatively, this diamond's crown angle is likely to produce a lot of brilliance (white sparkle). At the same time, it will likely be at the expense of dispersion (spectral bliss/fire).

In contrast, a crown angle between 34.3 and 35° will produce a virtual balance of sparkle factor. That is preferable because you'll see the full-spectrum of sparkle, whether from Blue Nile or Costco Diamonds.

Proportions of Costco Diamonds:

Costco Diamonds vs Blue Nile Engagement Rings.

Petite Micropavé Engagement Ring by Blue Nile.

The Costco diamond above has a 59% table diameter. That is too large given the shallow crown angle and will negatively impact light performance.

For one thing, it can make the arrows pattern look thin and spindly. It's also likely to create a lot of obstruction under the table facet.

Under normal circumstances, the pavilion angle of 40.8° will produce a high volume of light return. However, each piece of the diamond works in conjunction with the other parts. Hence the joke about one plus one equals three.

I'm sure you can see why I can't recommend this Costco diamond. Given these points, it should be clear that the GIA Excellent cut grade parameters are too broad. Although this may be true, the specifications for other Costco diamonds might be better.

Blue Nile Diamond Review, GIA 2137840617:

Blue Nile Diamond.

How does the Costco diamond above compare with what I was able to find at Blue Nile? In like manner, the crown angle of this 1.13 carat, G-color, VVS-2 clarity, GIA Excellent cut diamond from Blue Nile is a bit shallow.

However, the crown angle of 34 degrees is preferable and should produce better sparkle. According to the GIA, this diamond has a total depth of 59.3% and a 58% table diameter.

The pavilion angle of 40.8 degrees should produce a high volume of light return. Simultaneously, the 34° crown angle creates a reasonably good balance of brilliance and dispersion.

Double Check the Crown Angle:

Popular Shapes Blue Nile vs. Costco Diamonds.

Pick Your Favorite Diamond Shape from Blue Nile.

The 34° crown angle on the Blue Nile diamond above is likely to produce slightly more brilliance than dispersion. That means that this diamond will probably exhibit a little more white sparkle than fire.

The difference in sparkle between a crown angle of 34 - 34.3 degrees is slight by the same token. The odds are that most people are not likely to notice the difference without some coaching.

The proportions of this diamond are within the spectrum for the AGS Ideal-0 cut grade. On the contrary, the proportions of the Costco Diamonds above are not within the ideal range.

Besides, I don't know how the IGI came up with this Costco diamonds ring's value. However, I assume that it represents their estimate of full-blown retail and includes the ring's cost. Consequently, the Blue Nile diamond is selling for $11,301 and offers better performance.

If you're keeping score, it's currently Blue Nile: 1 / Costco: 0

Costco Diamonds Review - GIA #5126183164:

  • IGI graded (ring valuation).
  •  1.26 carat, G-color, VVS-2 clarity, GIA Excellent cut diamond.
  • 950 Platinum rating, 1.58 carats combined total weight.

According to the GIA, this Costco diamond has a total depth of 60.0% and a 59% table diameter. The diamond also has a 33° crown angle offset by a 41-degree pavilion angle. The girdle edge is medium to slightly thick and faceted, and the culet size is none.

Costco Diamonds GIA 5126183164

This diamond has an overall grade of GIA Excellent and proportions within the Ideal spectrum. Be that as it may, the crown angle of 33 degrees is much shallower than I prefer.

Despite that fact, some jewelers think that a shallow crown is a reasonable offset for a steep pavilion. I'm not one of those people because I know that this combination has drawbacks.

The pavilion depth of 43.5% is too steep to produce an exceptional light return. Consequently, it's the critical tipping point where light begins not to strike the pavilion facets optimally. This Costco diamond is likely to leak a lot of light as a result.

Blue Nile vs. Costco Diamonds Prices:

Ritz Round Halo Setting Blue Nile

Blue Nile Ritz Round Halo Setting.

Unfortunately, Tina didn't provide me with the Prices for these Costco diamonds. For this reason, I don't know how they compare with Blue Nile diamond prices. Be that as it may, this 1.27 carat, G-color, VVS-2 clarity, GIA Excellent diamond from Blue Nile has better proportions.

This Blue Nile diamond has a total depth of 61% and a 57% table diameter. The pavilion angle of 41 degrees is still steeper than I prefer. However, the 43% pavilion depth will produce a better light return than the 43.5% on the Costco diamond.

At the same time, the crown angle of 34.5° should produce a virtual balance of brilliance and dispersion. With this in mind, this one should exhibit better light return and sparkle than the Costco diamonds above. The current price is $13,862.00 for this GIA Excellent round diamond from Blue Nile.

The score is now Blue Nile: 2 / Costco: 0

Costco Diamonds Review: GIA #2131719297

  • IGI graded (ring valuation of $19,610.00).
  •  1.13 carat, H-color, VVS-2 clarity, GIA Excellent cut diamond.
  • 950 Platinum rating, 1.45 carats combined total weight.
Costco Diamonds Review.

The proportions diagram for this GIA Excellent round diamond from Costco is to the left. As can be seen, the pavilion depth is 43.5% once again.

Remember, this is the critical tipping point where the volume of light return begins to drop. With this in mind, we want to avoid that 41°/43.5% pavilion angle/depth combination.

On the positive side, the 34.5° crown angle should produce a virtual balance of brilliance and dispersion. However, that doesn't matter because the 43.5% pavilion depth is a deal killer.

Avoid the 43.5% Pavilion Depth:

Buying a round diamond with a 43.5% pavilion depth is like purchasing a 100-watt lightbulb that only delivers 1000 lumens instead of the standard 1600.

Besides, the total depth of 62.1% has a hidden cost that most people don't consider. If the total depth measurement is too deep, it can negatively impact the diameter. In that case, you're paying a premium for carat weight in the form of total depth instead of visible surface area.

In other words, the visible outside diameter of your diamond shrinks as the total depth increases. That is why I recommend keeping the total depth between 59 - 61.8% for round Costco diamonds.

Blue Nile Diamond Review, GIA 5131940712:

Blue Nile Diamond.

At present, this 1.12 carat, H-color, VVS-2 clarity, GIA Excellent round from Blue Nile is the best comparison to the previous Costco diamonds.

To the left is the clarity photograph for this diamond from Blue Nile. This diamond has a total depth of 61.3% and a 57% table diameter.

The 40.6° pavilion angle should produce a high volume of light return. The 35° crown angle should simultaneously create a virtual balance of brilliance and dispersion.

The visible outside diameter of this diamond is more significant because of the shallower total depth. This diamond measures 6.68 - 6.72 mm, so it has an average outside diameter of 6.70 millimeters.

Accounting for Total Depth:

Costco Diamonds vs. Brian Gavin Engagement Rings.

Spectacular Sparkle from Brian Gavin Diamonds.

While the 1.13 carat from Costco measures 6.66 - 6.68 millimeters and has an average outside diameter of 6.67 millimeters. Consequently, the smaller Blue Nile diamond faces up larger.

For this reason, I prefer a total depth between 59-61.8% for round brilliant cut diamonds. For information on fancy shape diamonds, refer to this article on calculating proportions.

By the way, this Blue Nile diamond is currently selling for $8,654.00. That seems better than the price of Costco Diamonds.

The current score is Blue Nile: 3 / Costco: 0 (that means something in baseball).

Are Costco Diamonds Good Quality?

Blue Nile Studio Engagement Rings.

Blue Nile Studio Engagement Rings.

Under the circumstances, you might be thinking that Blue Nile diamonds are better than Costco diamonds. Although this may be true, it also might not be because this game is rigged.

In the first place, the Costco diamonds I'm reviewing are the ones that our client is considering. In that case, there is a good chance they won't meet my selection criteria.

On the other hand, the odds are high that my search will yield better results. After all, I'm a diamond buyer by profession with 30+ years of trade experience.

If you search Blue Nile, you'll see plenty of options with proportions similar to Costco diamonds. In that case, you'll find that most of their diamonds don't make it.

This Costco Diamonds vs. Blue Nile Review Seems Skewed:

The Simpson's Amazon

To put it differently, when I search for diamonds, the goal is to cherry-pick the best options available. That means I'm not going to mention Blue Nile diamonds that aren't better than Costco diamonds. That's just common sense. LOL, I guess I cheated!

DOH! Nevertheless, it's essential to keep things in perspective. In the first place, these are the Costco diamonds that interest my client. To that end, I don't believe that it's my fault that they don't meet my standards.

Try to see the situation from my vantage point. The client chose these diamonds from Costco, not me. Likewise, the comparison between Blue Nile and Costco Diamonds is at the client's request.

With that in mind, it's in my client's best interest for me to provide her with better options. She can always use the insight herein to select other Costco diamonds that might perform better than these.

Brian Gavin vs. Blue Nile vs. Costco Diamonds:

Brian Gavin Engagement Rings vs. Costco Diamonds

Diamond Engagement Rings from Brian Gavin.

If you're looking for the most spectacular looking diamond possible, here's a little advice. The first thing to remember is that diamond cut quality dictates light performance.

That means that the combination of proportions and optical precision will determine the light return and sparkle intensity. To put it differently, you're not going to get the best performance from a diamond with less than perfect make.

Although this may be true, the proportions of a diamond are only one piece of the puzzle. The degree of optical precision has more influence on the sparkle factor. That is the consistency of facet shape, size, and alignment from the perspective of 360-degrees.

Proportions + Optical Precision = Sparkle Factor.

Brian Gavin Signature diamond.

In that case, you might consider dropping down in clarity so that you can enjoy better performance. It's a common misconception that higher clarity diamonds look better than lower clarity diamonds.

This 1.245 carat, I-color, VS-2 clarity, Brian Gavin Signature diamond will look the same as a VVS-2 without magnification. Consequently, this diamond's proportions and higher cut quality will produce a sparkle factor that is more vivid and intense.

The 40.8° pavilion angle will produce a higher volume of light return. The 34.8° crown angle will simultaneously create a virtual balance of brilliance and dispersion. The higher degree of optical precision will produce sparkle that is more vivid and intense.

Brian Gavin Knocks It Out of the Park!

3.50 carat, E-color, VVS-1 clarity, Black by Brian Gavin Diamond.

Sizzling Sparkle of Black by Brian Gavin Diamonds.

Although this may be true, there is nothing like photographic evidence to seal the deal. Because of that reality, take a look at the reflector scope images on the diamond details page.

The ASET and Ideal Scope images indicate the highest volume of light return. Another critical point is how evenly light appears to be reflecting throughout this diamond. Be sure to note the even distribution of hue and saturation.

The diamond also exhibits a picture-perfect pattern of hearts and arrows. That is a clear indication of a higher degree of optical precision. Consequently, it can take up to 4x longer to polish an ideal cut diamond to this degree of perfection.

Costco Diamonds Review Update:

Blue Nile Diamond Search.

Upon reading this post, Tina asked me to run a new search for Blue Nile and Costco diamonds. This time we will search using my selection criteria to ensure success.

You can see how I set the search parameters on Blue Nile to the left in that case. We'll be searching for diamonds with a total depth between 59 - 61.8% and a table diameter between 53 - 58%.

Even though this will narrow down the field of possibilities, it does not guarantee success. After all, the examples above prove that the parameters for the GIA Excellent rating are too broad.

Unfortunately, Blue Nile does not enable us to search by crown or pavilion angle measurements. That means that we will have to open up the details page for each diamond in the results.

Given that fact, you'll need to right-click your mouse over each line on the list. Then choose the option to open the page in a new tab of your browser. That will enable us to see whether the crown and pavilion measurements are within the range we seek.

Remember that you're looking for diamonds with a crown angle between 34.3 – 35.0° offset by a 40.6 - 40.9 degree pavilion angle.

Blue Nile Diamond Review, GIA 2151795921:

Blue Nile GIA Excellent diamond.

Take a look at this 1.28 carat, G-color, VS-2 clarity, GIA Excellent cut diamond from Blue Nile. As you can see on the diamond grading report below, the proportions meet my selection criteria.

This diamond has a total depth of 60.3% with a 58% table diameter. The pavilion angle of 40.8° should produce a high volume of light return. The 34.5° crown angle should also create a virtual balance of brilliance and dispersion.

The 75% Lower Girdle Facet length should produce an arrows' pattern with the right balance. This combination of proportions and LGF usually creates sparkle that is larger, bolder, and brighter.

In comparison, an LGF between 80-82% usually makes sparkle smaller in size and less intense. It's essential to know that the GIA Laboratory rounds the lower girdle facet length off to the nearest five percent. That means that an LGF of 78% will appear 80% on a GIA diamond grading report.

HCA Score of 1.3 + Tolkowsky Proportions:

Blue Nile Engagement Rings Roundup vs. Costco Diamonds.

Which Blue Nile Engagement Ring Is Your Favorite?

In this case, the diamond proportions are in the "sweet spot" for the zero ideal cut proportions rating. The proportions are also within the spectrum for the Tolkowsky Ideal Cut rating.

Under those circumstances, it's not surprising that this diamond also scores well on the Holloway Cut Adviser. Specifically, it scores 1.3 Excellent for Light Return, Fire, Scintillation, and Spread.

To clarify, the total depth of 60.3% is why this diamond scores well on the HCA for spread. If the total depth were 60.4% and higher, then the HCA score would only be very good for spread.

Review of Blue Nile Diamond, GIA 2151770873:

Blue Nile GIA Excellent Diamond.

This other 1.28 carat, G-color, VS-2 clarity, GIA Excellent cut round diamond from Blue Nile meets my proportions criteria.

The 40.8 degree pavilion angle should produce a high volume of light return. Simultaneously, the 34.5° crown angle should create a nice balance of brilliance and dispersion.

The total depth of 61.5% and 55% table diameter is in line with my expectations, and the 75% LGF should produce substantial sparkle.

Although this may be true, I do not recommend that you buy this diamond. The reason is because of the inclusions within it. According to the key to symbols under the plotting diagram, this diamond contains the following clarity characteristics: crystal, cloud, knot, feather, and needle.

Consequently, a knot is an included diamond crystal that breaks the surface. In this particular instance, the knot appears on the lower plotting diagram.

Look for the small red and green circles to the left of the pavilion main facet in the 12 o'clock position. Knot inclusions pose a potential durability risk, as you will discover below.

Inclusions We Reject:

  • Bruise.
  • Cavity.
  • Chip.
  • Cleavage.
  • Crystal on Surface.
  • Etch Channel.
  • Flux Remnant.
  • Knot
  • Laser Drill Holes.

If a diamond contains any of the inclusions above, we reject it automatically because these types of inclusions might pose a durability risk. That is not to say that they are a problem, but there is that potential. Under those circumstances, we prefer to err on the side of caution, especially when there are so many other options to consider.

Blue Nile GIA Excellent Cut Diamond Review:

GIA Excellent Blue Nile Diamond.

This 1.29 carat, G-color, VS-1 clarity, GIA Excellent cut round from Blue Nile doesn't quite meet my proportions criteria. As shown on the diamond grading report below, the crown angle is only 34 degrees.

I will occasionally consider diamonds with a 34-degree crown angle, but only if the pavilion angle is spot-on. The reason is that the GIA rounds off the crown angle to the nearest half a degree. 

Blue Nile Halo vs. Costco Diamonds and Jewelry.

Choose from 200+ Halo Settings on Blue Nile.

That means that a crown angle of 34.2° will appear 34-degrees on the diamond grading report. Under those circumstances, a crown angle of 34.3° shows 34.5° on a lab report from the GIA.

Likewise, a crown angle of 33.8° will appear 34-degrees on a GIA diamond grading. With this in mind, considering diamonds like this represents a bit of a gamble. I might think about this diamond if the crown angle is on the high side of 34 degrees.

However, I usually don't give diamonds like this a second glance because I'm not particularly eager to gamble. I benefit from seeing thousands of diamonds and prefer a better balance of brilliance and dispersion.

At the same time, most people don't have the experience of comparing diamonds side-by-side. That means that they are buying blind for the most part. Given these points, I strongly recommend adhering to the proportions in our Five Minute Tutorial.

Buying Blue Nile & Costco Diamonds By The Numbers:

Diamond proportions are a critical part of the equation, as shown in the preceding examples. In that case, we can use the proportions to narrow down the field of possibilities.

Be that as it may, knowing the proportions of the diamond will only get you so far. Consider the proportions of this 1.24 carat, E-color, VS-2 clarity, GIA Excellent cut diamond from Blue Nile as an example.

Blue Nile Diamond clarity.

According to the GIA, this diamond has a 40.8 pavilion angle; thus, the light return should be spectacular. To say nothing of the brilliance and dispersion that the 34.5° crown angle should produce.

The lower girdle facet length looks like 78% to me, which the GIA rounds off to eighty percent. With this in mind, this diamond should exhibit a high volume of light return. At the same time, it should produce a virtual balance of brilliance and dispersion.

So, why does this diamond look dark in the middle? The most likely reason is a lack of optical precision that would be evident in an ASET Scope image.

Using the Holloway Cut Adviser to Pick Costco Diamonds:

Holloway Cut Adviser.

HCA Score for this Blue Nile Diamond Review.

The Holloway Cut Adviser (HCA) gives this diamond a score of 1.3 Excellent due to the proportions. In this case, the diamond scores excellent for light return, fire, and scintillation.

As you may recall, the HCA scores a diamond very good for spread unless the total depth is <60.3%. Although this may be true, I'm going to demonstrate why diamond proportions are only the beginning.

In the first place, Gary Holloway describes the HCA as a diamond elimination tool. Therefore, you should use the HCA to narrow down the options and reflector scope images to eliminate undesirable possibilities.

How to Use the Ideal Scope to Identify Light Leakage:

Ideal Scope Blue Nile

From time to time, I can find reflector scope images for Blue Nile diamonds even though they don't provide them. That is one of the hidden benefits of my trade status.

Here's the Ideal Scope image for this 1.24 carat, E-color, VS-2 clarity, GIA Excellent cut diamond from Blue Nile. The light pink semi-transparent sections under the table facet indicate light leakage.

At the same time, it's easy to see that light is not reflecting evenly throughout this diamond. This type of revelation can be shocking to people because they assume GIA Excellent guarantees performance.

 Hidden Insight from the AGS ASET Scope:

Blue Nile ASET Scope.

The ASET Scope image for this 1.24 carat, E-color, VS-2 clarity, GIA Excellent cut diamond from Blue Nile tells a similar story. It reveals light leakage identical to the Ideal Scope image shown above.

We can also use ASET to determine how evenly light is reflecting throughout the diamond. As a result, we can see how unevenly this diamond reflects light. In other words, the colors red, green, and blue do not reflect throughout this diamond evenly.

That is an indication of the degree of optical precision rather than proportions. By the way, be sure to read the article "What do the different colors of ASET mean?"

These reflector scope images are the most compelling evidence in support of their necessity. It's essential to realize there is more to buying an engagement ring than whether it's from Blue Nile or Costco Diamonds. In the first place, neither of these companies produce diamonds. Both Blue Nile and Costco Diamonds are retailers, not manufacturers.

Another critical point to remember is that each reflector scope image has a specific purpose as the design reflects. While the scopes might reveal light leakage or consistency to varying degrees, they are not interchangeable. In that case, be sure to get both an ASET and an Ideal Scope image.

Searching for Costco Diamonds Online:

Diamond Shapes Blue Nile vs. Costco Diamonds

Blue Nile Offers All the Popular Diamond Shapes.

I'm not going to search for Costco Diamonds since they don't seem to offer loose diamonds online. However, I will look over the details for any Costco Diamond you may be considering. Just send me the diamond grading report number for evaluation.

Consequently, I am also happy to help you compare Costco Diamonds with any other brand. Just remember that light performance and sparkle factor are the result of proportions and optical precision.

In that case, you'll want to keep an eye on the proportions and the reflector scope images. Otherwise, you may as well be trying to pick Costco Diamonds while wearing a blindfold. Of course, that statement is true of practically every other brand, so take it with a grain of salt.

Todd Gray

About the author

A mad scientist with a passion for improving diamond cut quality to maximize light performance and sparkle factor. I speak geek in degrees of optical precision between bouts of freediving. My ghostwritten ramblings haunt the rabbit holes of information found on many diamond vendor sites. Diamond buyer, author, consultant, errant seeker of deep blue water.

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  1. Hi. I’m helping a family member look for rings and they were looking at this wedding set from Costco (price is right on point for the budget). I did notice that it made no note of the diamond certification (I sent Costco an email and am waiting to hear back). But I’d love to know your thoughts and perhaps recommendations for something similar. Thanks!

    1. Thank you for your inquiry. The problem that I have with the way Costco describes their jewelry online, is that they don’t provide a copy of the diamond grading report for the diamond that will actually be used in the ring; so in this case they indicate that the center stone will be a 0.70 carat, I-color, VS-2 clarity, round diamond, they don’t even really indicate whether it will be lab graded or not, simply that their team of gemologists inspect every piece of jewelry, blah, blah, blah; so there is no way to provide an accurate comparison, since the proportions of the diamond are unknown; we don’t know whether they are grading by GIA standards, AGSL standards, IGI standards, EGL standards, their own standards, etc.; and we don’t know the overall cut grade of the diamond; or the fluorescence rating; and all of this affects the price of the diamond. In fact, the proportions rating and overall cut grade of a diamond can affect the market price by as much as 60% so this is a rather important thing to know.

      Please send me a copy of the diamond grading report when you get a chance, you can email it to me directly at diamonds[at] or post the diamond grading report number here if is graded by the AGSL, GIA, HRD, or IGI and I can look it up for using the report check feature offered on their web site; however I would only accept options graded by AGSL, GIA, or HRD, personally.

  2. Hello sir, I am in the hunt for a nice diamond and came across your posts. You are a Godsend! Do those search parameters apply to any size round stone? Aside from the range values…what would be the most optimum dimensions that would be the “perfect stone” in your professional opinion? I want the rock to sparkle like nobody’s business…:)

      1. I am not able to find the filter for crown angle and pavilion angle on bluenile’s advanced filter for diamonds….am I missing something?

        1. Blue Nile (and everybody else that I know of) does not offer the ability to filter diamonds by crown and pavilion angle, they only offer the option to limit the search results by total depth and table diameter, which I recommend keeping between 59 – 61.8% total depth for rounds, with a table diameter between 53 – 58%; then you’ll need to open up every one of the diamond details pages, by right clicking on the “more details” tab and clicking “open in new tab” and then visit each page to open and review the diamond grading report; I recommend eliminating all options that do not have a pavilion angle between 40.6 – 40.9 degrees, offset by a crown angle between 34.3 – 34.9 degrees; you can stretch things to 41.0 / 35.0 degrees if no other options are available, but this takes a bit more experience. I’m happy to look at the options for you if you’d like to submit a request via my Diamond Concierge Service, the service costs you nothing (I’m compensated via affiliate agreements with the companies I work with) and the 25+ years experience I have buying diamonds will definitely benefit you…

          1. Your knowledge is greatly appreciated…I will use that service once I narrow my searches. Thank you!

  3. Todd,

    I want to buy 3-carat stud earrings for my wife. This one #923431 from Costco is $23K.

    Is this a good price or should I look for something similar in Blue Nile.

    1. The challenge as I see it is that Costco does not provide any insight as to the cut quality for the three-carat total weight diamond earrings sold by Costco, they merely state on the web site that the diamonds are VS-2 clarity and I-color and that they might be graded by either the GIA or IGI gemological laboratories, and one of those things is not like the other in my personal opinion.

      This paramount to buying a car online for $23k, and only knowing whether it has two or four doors and the paint color; the running condition of the motor (visual performance), and the condition of the body (proportions, polish, symmetry) is entirely unknown; the description might as well read “two round shiny rocks, polished to sparkle, weighing three-carat total weight, graded by this or that gemological laboratory, $23K”.

      Suffice to say that there is room for a great deal of improvement in how Costco markets diamond jewelry online; why doesn’t Costco post diamond grading reports for the pairs of three-carat diamond earrings that they offer online? Apparently, the diamonds are graded by the GIA or the IGI, so it should not be that much of a challenge; but of course, they’re not selling you a specific pair of earrings, once again, they expect you to buy blind, fork out $23k, and they get to send you any pair of 3-carat t.w. diamond earrings that fit the bill; that might be all right with toilet paper and pens, but it doesn’t work all that well for diamonds as far as I’m concerned.

      Since you mentioned Blue Nile, I ran a search for round ideal cut diamonds on Blue Nile, weighing between 1.50 – 1.60 carats, I-color, VS-2 clarity, with advanced parameters set to only include diamonds with a total depth between 59 – 61.8% and a table diameter between 53 – 58% with an overall cut grade of either GIA Excellent or AGS Ideal; this provided me with twelve options, which I narrowed down to the following two pairs of diamonds for earrings:

      This 1.51 carat, I-color, VS-2 clarity, round diamond from Blue Nile which measures 7.36 – 7.40 x 4.53 mm, paired up with this 1.53 carat, I-color, VS-2 clarity, round diamond from Blue Nile, which measures 7.37 – 7.40 x 4.56 mm.

      Both diamonds have a pavilion angle of 40.8 degrees, which will provide a high volume of light return, which is offset by a crown angle of 35.0 degrees. That will provide a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle) and have an overall cut grade of GIA Excellent.

      The combined price of the diamonds before the cash/wire transfer discount is $22,133.00 and you can have them set in four prong platinum stud style earrings from Blue Nile for $250.00 and I’m sure that screw-back posts are an available option; thus I’m confident that not only can you beat the price offered by Costco, but you can also buy with the confidence of knowing exactly what you are paying for.

      If you want something a little larger, you can match this 1.56 carat, I-color, VS-2 clarity, round diamond from Blue Nile, which measures 7.45 – 7.48 x 4.61 mm, up with this 1.58 carat, I-color, VS-2 clarity, round diamond from Blue Nile, which measures 7.45 – 7.47 x 4.60 mm; both of which have an overall cut grade of GIA Excellent, with a 41.0 degree pavilion angle. That should provide a high volume of light return, and which is offset by a crown angle of 34.5 degrees, which should provide a virtual balance of brilliance and dispersion; the total price of this pair is $23,475.00 before the cash/wire transfer discount, the settings are referenced above.

    1. Thank you for your inquiry, the ring which you reference from COSTCO is what is known as a princess three stone trellis style engagement ring, the total weight of the ring is 2.00 carats, with the center stone weighing around 1.00 carats and the two accent diamonds weighing 1.00 carats total weight, or around 0.50 carats each, the listing on COSTCO indicates that the diamonds are I-color, and VS-2 clarity. I used the ring builder feature on Blue Nile to put together this trellis style 3 stone ring with princess cut diamonds, the diamond quality and total carat weight is the same. However, I think that the diamond cut quality might be a bit better.

  4. Hi Todd,

    I am planning to buy a 14k white gold hoop earrings from Blue Nile but I am trying to compare it with what Costco has?

    Small hoop earrings 14k from Blue Nile.

    #11766025 – hoop earrings 14k from Costco.

    I understand the specifications are different but which do you think is a better buy? I am leaning towards Blue Nile just for the fact that the earring looks better. But on the other hand, the diameter of the earring on Costco is obviously better which means more gold. I know this post is not about diamonds but any feedback will be helpful.



    1. Hi Dave,

      One thing to keep in mind is that the gold weight of a piece of jewelry is not necessarily relative to the size, especially with items like earrings such as these, which are usually made of hollow construction so that they don’t weigh down the ears… therefore it isn’t possible to determine which set of earrings represents a better buy, without knowing the gram weight of each piece, speaking strictly from a perspective of gold weight = market value; however in truth the value is relative, best based upon which pair of earrings appeals to your personal sense of style.

      P.S. I realize that I responded to this via email, but thought that other people would benefit from the response. All the best!

    1. Thanks for the update Tina! All right, so the ring from Costco which contains the 1.26 carat, G-color, VVS-2 clarity, GIA 3X cut diamond [GIA #5126183164] and an additional 0.32 carats total weight of accent diamonds, for a combined total diamond weight of 1.58 carats is priced at $16,000.00 and if we look at the option which I found from Blue Nile which is priced at about $14,100.00 it’s reasonable to assume that the difference in price is partially due to the cost of the setting, which can vary in price depending on the ring style, alloy type, metal weight, shape of accent diamonds, number of accent diamonds, quality of the accent diamonds, etc. For instance, I found this Princess Cut Channel Setting in 14k white gold from Blue Nile with a half carat total weight of accent diamonds for $1,480.00 the color of the accent diamonds is I-color, but the clarity is only SI-2; and then there is this Halo Setting from Blue Nile which is an extremely popular ring style right now, which features a half carat total weight of round diamonds of the same quality which is selling for $1,750.00 or you can choose something higher in overall production quality, that is custom made to order like this which has a significantly higher carat weight of 0.75 carats in a higher clarity of VS and a higher color range of F/G and sells for $3,260.00 which makes since because it’s essentially twice the diamond weight and higher in quality ~ the point that I’m trying to make is that the price of a setting is based on a series of minute details that factor into the final price of the setting… so the setting from Brian Gavin is not “more expensive” it is simply a different setting, comprised of different components. If a less expensive setting is desired, simply select one with a different carat weight, such as this Fishtail Pave setting from Brian Gavin which has a total weight of 0.42 carats of F/G color, VS clarity, accent diamonds and is priced at only $2,100.00

      Keep in mind that a lot of retail jewelry stores and companies like Costco like to “bundle” diamonds and engagement rings into individual units of sale which are priced as a unit, I prefer to shop for diamond engagement rings by individual component, beginning with the diamond and then the ring which provides me with better control over the quality of the diamonds contained in the ring, but also gives me a better idea of exactly what I’m paying for what…

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