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Essential Guide: Diamond Prices vs. Quality


May 22

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Diamond Prices vs Quality:

“There’s no such thing as a free lunch.” You can find a cheaper price but what are you giving up?

It’s a common mistake made by a lot of newbie diamond buyers and a lot of retail jewelers are getting rich off of their ignorance. The mistake we’re referring to is assuming that all ideal cut diamonds are the same based on the basic details provided on the diamond grading report.

Which is another topic entirely, the difference between diamond grading laboratories such as the AGS, EGL, GCAL, GIA, HRD, IGI, and others. But we’ll leave that topic for another article because this one is about making sure that you don’t get ripped off buying a diamond simply because it’s AGS Ideal or GIA Excellent cut.

AGS Ideal versus GIA Excellent cut:

The first mistake that a lot of diamond buyers make is assuming that the AGS Ideal and GIA Excellent cut grading parameters are the same.

I’ll pause a moment to let the meaning of that sentence sink deeply into the recesses of your mind…

Wait. What?!?! That’s right. The AGS Ideal and GIA Excellent cut diamond parameters are not the same because only the American Gem Society Laboratory (AGSL) grades diamonds for light performance using angular spectrum evaluation technology (ASET). The GIA Gem Trade Laboratory does not have the ability to grade diamonds for light performance.

Which means that you’re missing a significant piece of the puzzle when considering GIA Excellent cut diamonds, unless the vendor provides an ASET Scope image. Unfortunately, most vendors online (and certainly most jewelry stores) do not provide their customers with ASET Scope images because that would make it easier for you to see the difference between the light performance of their diamonds and ours. 

All Ideal Cut Diamonds are NOT Created Equal:

It’s a bold statement, but it’s true.

The proof is in the pudding as they say. Let’s take a look at the 1.01 carat, E-color, VS-1 clarity, GIA Excellent cut diamond that sparked this flame.

One of our clients asked why this diamond is priced so much lower than a Black by Brian Gavin diamond of comparable quality. Those are his words, not ours… Because one look at the clarity photograph provided by the vendor and we already knew that this diamond is not comparable to a Black by Brian Gavin diamond.

We didn’t even need a reflector scope image to make the call because it’s blatantly obvious that this “GIA Excellent cut diamond” is leaking light. You just have to know what to look for, but this particular client was stuck on the details provided on the diamond grading report.

“The overall cut grade is GIA Excellent and the proportions are comparable to the Black by Brian Gavin diamond that I’m considering…”

What They Don’t Tell You About Diamond Proportions:

Fair enough. It might be reasonable for people to assume that two ideal cut diamonds are “comparable” because the proportions are within the same range:

Overall Cut Rating:

GIA Excellent

AGS Ideal-0

Carat Weight:

1.01 carats

1.02 carats

Clarity:

VS-1

VS-1

Color:

E-color

E-color

Fluorescence:

None

Negligible

Measurements:

6.43 – 6.47 x 3.97 mm

6.44 – 6.47 x 3.99

Total depth:

61.6%

61.8%

Table diameter:

57%

56.4%

Crown angle:

35 degrees

34.7 degrees

Crown height:

15%

15.1%

Pavilion angle:

40.8 degrees

40.8 degrees

Pavilion depth:

43%

43%

Star facets:

50%

52%

Lower girdle facets:

80%

76%

Culet size:

None

Pointed

As a matter of fact, both of these diamonds have proportions that are within the middle or “target zone” of the spectrum designated for the AGS Ideal-0 proportions grade.

From that perspective, it does appear that the diamonds are comparable. However, that is where the similarities between these two “ideal cut diamonds” ends.

Black by Brian Gavin Diamonds Set the Standard for Light Performance:

One look at the ASET scope images provided for these two diamonds is all that is necessary to see that they are not really comparable.

The ASET Scope image provided for the 1.02 carat, E-color, VS-1 clarity, Black by Brian Gavin diamond pictured on the left, proves that this diamond is producing the highest degree of light performance. Notice how evenly light is reflecting throughout the diamond, as indicated by the different colors created by the ASET Scope.

It doesn’t take a rocket scientist to see that the GIA Excellent cut diamond on the right is light years behind the Black by Brian Gavin diamond in terms of performance. The ASET Scope image reveals a “transparent window” which indicates full-blown light leakage under the table facet.

There is also a moderate amount of light leakage visible in the four to six o’clock region of the table facet. A slight amount of light leakage is also apparent throughout the rest of the diamond as indicated by the semi-transparent region all the way around the edge of the table facet.

And then, there is the heavy concentration of “secondary brightness” indicated by the green splotches that run throughout most of the crown facets. In an ideal world, the upper girdle facets in that region of the diamond should appear to be red in an ASET Scope image.

ASET vs Ideal Scope Images (similarities & differences):

As you can see, the Ideal Scope images provided for the Black by Brian Gavin and the GIA Excellent cut diamond reveal different things than the ASET Scope images.

To begin with, the image provided for the GIA Excellent cut diamond on the right is not actually an Ideal Scope image. Nope. It’s actually just a picture of the crown view of the diamond as seen through a hearts and arrows viewer.

The Ideal Scope image provided for the Black by Brian Gavin diamond on the left enables us to verify that the diamond is not leaking light to any significant degree. While the image provided for the GIA Excellent cut diamond on the right is only intended to verify the arrows pattern.

However, that’s not going to stop us from pointing out that the diamond is leaking light extensively under the table facet as indicated in the relative one o’clock position.

At the same time, you’ll notice that it is not as easy to determine how evenly light is reflecting throughout these two diamonds using the Ideal Scope and arrows images. This is because the ASET and this particular H&A Scope both rely on the color red to filter the light entering the diamond.

While the ASET Scope uses the colors red, green, and blue to distinguish the differences between light entering the diamond from different vantage points. With this in mind, you’ll want to be sure to compare apples to apples and oranges to oranges by insisting on both ASET and Ideal Scope images for any diamonds you are considering.

“It’s all in the hearts…” ~ Brian Gavin, 5th Generation Diamond Cutter

You might be wondering why the GIA Excellent cut diamond is leaking more light and exhibiting a lower degree of light performance than the Black by Brian Gavin diamond when the proportions are within the same range.

As fifth generation diamond cutter Brian Gavin is so fond of saying, “it’s all in the hearts.” Which is to say that the hearts pattern of a round brilliant cut diamond serves to demonstrate the degree of optical precision achieved by the cutter (at the trade level of evaluation) and ensures a higher degree of light return and sparkle factor when combined with the right proportions at the consumer level.

With that in mind, let’s take a look a “the hearts patterns” exhibited by these two diamonds:

Hmmm, those “hearts” exhibited by the GIA Excellent cut diamond look more like “lawn darts” but that won’t stop most people from mistaking it to be a hearts and arrows diamond. After all, there are some similarities between the outlines of hearts and lawn darts, but it’s pretty clear to us that cupid’s arrows missed the mark on this one.

But we digress. Let’s start out at the beginning. Take a look at the hearts pattern exhibited by the Black by Brian Gavin diamond on the left. Then take a look at the pattern of lawn darts exhibited by the GIA Excellent cut diamond on the right.

Do you see the difference in the consistency of shape, alignment, and spacing? Then take a look at the difference in the size and shape of the lawn darts (rabbit ears?) exhibited by the GIA Excellent cut diamond on the right.

And then there’s the extra spacing that is visible around the lawn dart in the relative one o’clock position, which also happens to be about half the size of the others.

Which is an indication that there is a distinct difference in the length of the lower girdle facets of this GIA Excellent cut diamond. And for the record, we’re not bashing on GIA Excellent cut diamonds, because we’ve also seen this kind of thing in a lot of AGS Ideal cut diamonds.

More specifically, in what universe would these two “ideal cut diamonds” be considered comparable? The differences between them are as clear as night and day.

Which brings us back around to the clarity photograph for this GIA Excellent cut diamond. That dark region that is visible under the table facet in the one o’clock region which is dark as night?

That’s the light leakage that is evident in the ASET Scope and Ideal Scope images (ahem, H&A Scope image) provided above. Diamonds are supposed to be bright white and full of light, unless it’s a fancy colored diamond. You don’t want to see this kind of light leakage in your diamond.

Which is why more and more people are choosing Black by Brian Gavin. Once you know what to look for, the difference is perfectly clear.

Price Differences Between Tiers of Diamond Cut Quality:

It’s a little-known fact, but the overall cut quality of a diamond can affect the price by as much as sixty percent. Which is why the standard GIA Excellent cut diamond referenced in this article costs less than the Black by Brian Gavin Hearts and Arrows diamond.

While both “ideal cut diamonds” are cut to the same “target range” of proportions, the Black by Brian Gavin diamond exhibits a higher degree of optical precision. The more precise degree of facet shape, size, and alignment of the facets on the surface of the diamond, creates a higher volume of light return and sparkle factor which is more vivid and intense.

From a technical perspective, a higher degree of optical precision also produces a higher number of virtual facets within the diamond. Which means that there will be a higher number of reflections within the diamond and that will produce more sparkle reflecting from the diamond.

Diamond cutters like Brian Gavin know that this degree of optical precision is the result of spending more time polishing the diamond. As a matter of fact, it probably took about four times longer to polish the Black by Brian Gavin diamond to this level of perfection.

It’s a difference worth paying for because it produces a higher degree of light return and sparkle which is more vivid and intense. Aren’t you glad you took the time to learn about the difference between different versions of ideal cut diamonds?

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