• Home
  • /
  • Diamond Buying Tutorial: 5 Minute Guide to Sparkling Success

In this diamond buying tutorial, we're going to show you how to buy diamonds for sparkle factor. With that in mind, we hereby throw caution to the wind and suggest diamond cutting is more of a science than an art. Although this position might upset a few diamonds cutters, the reality is that diamonds are three-dimensional geometric models.

In that case, it's a simple matter of geometry and the proportions will have a direct impact on light performance. While the consistency of facet size, shape, and alignment will dictate the size and intensity of the sparkle. In other words, the volume of light return will be in direct proportion to the pavilion angle. 

Diamond Buying Tutorial 5 Minutes to Success.

Corey Gray's Black by Brian Gavin Diamond Ring.

While the crown angle will determine the balance of brilliance (white sparkle) and dispersion (colored sparkle/fire). At the same time, the degree of optical precision will determine the size and intensity of the sparkle.

If you want to save a lot of time and get it right the first time, then you should just buy a Brian Gavin Signature diamond. After all, he cut the diamond for my wedding ring and my son's engagement ring.

As a matter of fact, that says a lot since I have 35+ years experience as a diamond buyer. Obviously that means that I know what to look for and the best places to find it. Consequently, my family buys their diamonds from Brian Gavin because they exhibit the most spectacular sparkle we've ever seen!

Standard Ideal Cut & Beyond:

To begin with, I want to encourage you not to make the same mistake that most people do. That is assuming that focusing on AGS Ideal and GIA Excellent cut diamonds is good enough. As a matter of fact, that overall cut grade is only the beginning from our perspective.

Diamond Buying Tutorial James Allen True Hearts.

James Allen True Hearts Diamond.

Here is the lab report for this 1.13 carat, I-color, VS-2 clarity, James Allen True Hearts diamond. Consequently, the proportions are within the range we recommend and the overall cut grade is GIA Excellent.

In that case, the 40.8 degree pavilion angle should produce a high volume of light return. While the 34.5 degree crown angle produces a virtual balance of brilliance and dispersion.

Although that may be true, the Ideal Scope image on the left reveals a moderate amount of light leakage. That is what the light pink and semi-transparent sections that the light green arrows are pointing to indicates. Under those circumstances, you can see why it's important to look beyond basic details on the lab report.

Of course, this is just one example from the James Allen True Hearts collection. Obviously, I chose this particular diamond to demonstrate the importance of looking beyond the basics of cut grade. Whereas there are other diamonds in that collection that exhibit better light return. Needless to say, that you should pay particular attention to the images to make the best choice.

Best Proportions a’ la Engineer:

You're in luck if this is the first diamond buying tutorial that you've read because you'll get started out on the right foot.  Because we're going to teach you to adhere to a very specific and tight range of proportions. After all, we've already proven above that ideal cut diamonds can still leak a lot of light.

Black by Brian Gavin Diamond.

Black by Brian Gavin Diamonds.

In that case, it makes sense to hedge your bets by focusing on the middle of the spectrum. After all, that is "the sweet spot" that is the middle of the target that you should be aiming for.

In other words, the proportions guidelines for the ideal cut rating encompass a range or spectrum of possibility. As such, there will be the middle target zone, and then the lower and outer edges where more leakage occurs.

Look at the ASET for this 1.806 carat, F-color, VS-1 clarity, Black by Brian Gavin Diamond. Notice how evenly light is distributed throughout the diamond and the consistency of hue and saturation. Here is a diamond that will outperform all others because it exhibits the highest degree of optical precision.

Don't fall into the trap of thinking that a diamond is going to perform well because of the overall cut grade. After all, you could drive a truck through the gap between the low and high-end of the scale!

(Maximum)2 Brilliance + Dispersion:

Given that a diamond is a three-dimensional model, it stands to reason that certain proportions perform better than others. As a matter of fact, the middle of the spectrum is the target for the ideal cut rating. Whereas the outer edges of that range are not going to perform as well.

In other words, we recommend the range of proportions below for a reason. That is because it tends to produce a high volume of light return and a virtual balance of brilliance and dispersion. If you deviate from the pavilion angle, then you'll see less light return. And if you deviate from the crown angle, then you won't see a balance of brilliance and dispersion.

Although that may be true, they like to say that there is an ideal cut diamond for every preference. In other words, you might prefer a diamond that exhibits more brilliance or dispersion. In that case, you might prefer a crown angle that is shallower or steeper than what we recommend. However, we strongly recommend that you do not deviate from the pavilion angle or the light return will suffer.

Proportions for this Diamond Buying Tutorial:

  • Total Depth between 59 - 61.8%.
  • Table Diameter between 53 - 58%.
  • Crown Angle between 34.3 - 35 degrees.*
  • Pavilion Angle between 40.6 - 40.9 degrees.
  • Lower Girdle Facets between 75 - 78%.**
  • Star Facet Length between 45 - 50%.*** 
  • Girdle thickness between thin and slightly thick.
  • Culet: AGS pointed or GIA none.

* Crown Angle:

Facet structure round brilliant cut diamond.

Diagram of Crown Facets.

The preferred range of crown angle for round brilliant cut diamonds provided above is clearly quite narrow. That is because it is most likely to produce a virtual balance of brilliance and dispersion. Especially when offset by a pavilion angle between 40.6 – 40.9 degrees.

Obviously, the idea is to help you find the best performing diamonds quickly and easily by eliminating the guesswork. Although that may be true, you might prefer a different balance of white and colored sparkle/fire. In that case, you should look at enough ideal cut diamonds to determine your preference.

** Lower Girdle Facet length:

Pavilion facet structure round diamond.

Diagram of Pavilion Facets.

In the first place, there is a reason why we recommend a Lower Girdle Facet (LGF) length between 75 – 78%. And that's because it tends to produce broad spectrum sparkle. Consequently, that is sparkle that is larger in size, and that looks bolder, brighter, and more vivid.

Whereas a longer LGF like 80-82% is likely to produce pin-fire type sparkle that is smaller in size and less intense. And lower girdle facets shorter than 75% are likely to make the arrow shafts look short and stubby. Needless to say that this will also affect the appearance of the arrows and the degree of contrast brilliance.

*** Star Facet Length:

Star facets are the small triangular shaped facets that are located on the crown section of the diamond. Just look for the triangles that are between the kite-shaped bezel facets. They're right on the outside edge of the edge of the table facet. As a matter of fact, they serve to round off the shoulders of the hearts in H&A Diamonds.

In that case, the star facet length is an integral part of the formula for Brian Gavin Signature Hearts and Arrows diamonds. However, you'll also notice that the measurements don't always line-up tightly with our preferred range. That's because the stars are "minor facets" that the cutters tweak to maximize performance.

For that reason, we tend to focus more on the consistency of the hearts pattern than the star facet length. Under those circumstances, it's perfectly acceptable for the star facet length to be between 40 - 58%. Assuming, of course, that the ASET Scope image verifies the light performance.

This Diamond Buying Tutorial Kills 99% of Rounds:

You're going to LOVE this diamond buying tutorial if you're looking for the best light performance. And you're going to HATE IT if you're a diamond cutter who has been relying on the broad-spectrum of proportions to sell ideal cut drek. After all, the range of proportions that we recommend eliminates 99% of the round diamonds produced in the average year.

In other words, this diamond buying tutorial focuses on the Top 1% of the annual production for round diamonds. While these super ideal cut diamonds are more like the Top 0.001%: 

Although that may be true, you'll see that these diamonds exhibit varying degrees of light performance. That's because they are turned on the wheel by hand. In that case, we rely on the insight provided by Advanced ASET and the H&A images to cherry pick the best of the best. Click on the banner below and use our Diamond Concierge Service to sift the wheat from the chaff.

Polish & Symmetry:

Obviously, it goes without saying that you want the best polish and symmetry grade possible. After all, it is a reflection of the degree of polish and facet alignment. Although that may be true, the symmetry grade on the diamond grading report is not the same as optical precision.

GIA Excellent Polish and Symmetry.

GIA Excellent James Allen True Hearts Diamond.

You'll may recall that optical precision is the consistency of facet shape, size, and alignment. Whereas meet-point-symmetry is what the lab report describes. Quite simply, that is based on how well the points of the facets meet-up at the junction points.

As a matter of fact, the reason why the James Allen True Hearts diamond above is leaking light is probably due to optical precision. Be that as it may, the Symmetry grade on the lab report pictured on the left is GIA Excellent. In that case, the polish and symmetry grade on the lab report is only the beginning.

Diamond Color:

As a matter of fact, what diamond color is best for you is strictly a matter of preference. In other words, one diamond color is not necessarily better than another. That's because one person might prefer diamonds that are cooler in tone, such as D-E-F color. While another person might prefer diamonds that are warmer in hue and saturation, such as K-L-M color.

At the same time, the perception of diamond color is subject to the environment and lighting conditions. For example, the color of the prongs that hold the diamond in place can affect the appearance by one color grade. Under those circumstances, we suggest that you consider the following to be a basic suggestion:

D-E-F colorless:

Colorless diamonds tend to be bright white and cooler in tone. They're going to deliver that surefire white similar the brightness of photo-grade paper. Obviously, it's a great choice if you've got the big bucks and don’t want to second-guess yourself.

G-H-I-J near-colorless:

As a matter of fact, G-color is a great choice because most people can't distinguish the difference between F-color. In that case, there is no need to pay a premium for color beyond the mental bump that F-color provides. Although that may be true, the difference between F-G color is visible under controlled lighting from a side-profile.

Under those circumstances, we still think of G-color as colorless. While it is apparent to us that H-I color is near-colorless because there is a little more warmth. Obviously, that statement is made in relationship to the comparison of H-I color to G-color. If we're sticking with the copy paper analogy, then H-I color is like bright white copy paper.

Whereas J-color begins to look a little more like the generic copy paper that is used for everyday purposes. As such, it tends to appeal to people who are looking to stretch their budget. In other words, you should consider J-color diamonds if you're willing to exchange a little color for carat weight. After all, it's still going to face-up white, it's just going to be a little warmer than H-I color. 

K-L-M light yellow:

As a matter of fact, I hate the term light yellow as it applies to white diamonds. That's because we tend to think of color as it relates to a box of Crayola Crayons. Although that may be true, diamond crystals are transparent and crayons are solid. In that case, there are distinct differences in the saturation of color.

F-K Color Diamond Comparison

F-K Diamond Color Comparison.

With that in mind, take a look at the F-K color Brian Gavin Signature diamonds on the left. In this case, the 3-stone ring on the left is my son's engagement ring. While the pavé solitaire on the right belongs to one of my clients.

Consequently, both rings are made of platinum and that tends to make the diamonds look whiter. That's because the color of the metal that touches the edge of the diamond is going to reflect throughout the stone.

Under those circumstances, you might consider buying a K-L-M color diamond that is light yellow. Because it's not going to face-up yellow like a Crayola Crayon. But, rather, it's more likely to exhibit a little bit of warmth and sparkle like the sun. In the event that sounds inviting, you should check out diamonds from the Brian Gavin Cape Collection.

Blue Fluorescence:

Brian Gavin Blue Diamond Buying Guide

Brian Gavin Blue Fluorescent Diamonds.

Obviously, no diamond buying tutorial would be complete unless it covers the phenomena of blue fluorescence. Although that may be true, the reality is that blue fluorescence is little more than an identifying characteristic.

From that perspective, our recommendation whether to buy a blue fluorescent diamond is solely based on whether or not you like the color blue. After all, a blue fluorescent diamond is going to glow neon-blue when exposed to black light.

Whereas a diamond with negligible fluorescence is not going to react to that light source. While out in the real world, both diamonds are going to look perfectly normal (white) under lighting conditions that don't involve black light. On that note, notice how the accent diamonds on the left reflect the color of the black light bulb.

Negligible, None, and Faint Blue:

As a matter of fact, low levels of fluorescence in the range of negligible to faint blue is not likely to have any effect. In that case, the fluorescence is nothing more than an identifying characteristic.

Note that the AGS and GIA laboratories evaluate diamonds for fluorescence in slightly different ways. The AGS Laboratory evaluates the diamonds in the face-up position as they will be viewed in a ring. While the GIA evaluates them from a side profile tilted back at a slight angle.

In case you're wondering, we think that the approach taken by the AGS Laboratory makes more sense. After all, you're going to be looking at your diamond in the face-up position. Although that may be true, the difference in methodology can create slight differences in the fluorescence ratings between the two laboratories.

For example, the AGS might give a diamond a fluorescence rating of negligible which is not enough to measure. While the GIA might deem the diamond to exhibit faint blue fluorescence from a side-profile. Be that as it may, the difference between negligible and faint blue is rather a mute point.

Medium Blue Fluorescence:

Generally speaking, medium blue fluorescence gives off a light lavender-blue hue under black light. When the fluorescent molecules are activated, they tend to enhance the natural color of most diamonds.

Diamond Grading Tutorial Medium Blue Fluorescence.

Brian Gavin Blue Fluorescent Diamond.

In other words, they can make them look whiter and brighter. That is because the blue fluorescence serves to filter out some of the yellow undertones that are present in diamonds of all color grades..

If it is any indication of what we think about fluorescence, most of the personal diamonds that we wear exhibit medium blue fluorescence. The photograph of the Brian Gavin Blue fluorescent diamond on the left shows medium intensity.

Some people worry that medium blue fluorescence might make their diamond look cloudy. As a matter of fact, the GIA determined that there is a negative impact in less than 2% of gem quality diamonds. In those cases, the level of fluorescence was very strong to distinct blue and over-blue.

Strong Blue Fluorescence:

In most cases, strong blue fluorescence is only going to improve the appearance of a diamond. Especially, if the diamond is in the near-colorless to faint yellow or warmer color range. As with medium blue fluorescence, it is unlikely that there will be any negative impact.

Note that we only recommend diamonds that exhibit blue fluorescence. In other words, we do not recommend diamonds with fluorescence in other colors. For example, green, red, orange, white, or yellow, because it can affect your perception of color. Of course, you might decide to buy such a diamond anyway for the novelty value.


In the first place, people tend to worry a lot about diamond clarity. On the one hand, I suspect that it's because they think that higher clarity diamonds perform better. Consequently, that might be true to some extent on some microscopic level, you're not going to see a difference once you go over VS-2 clarity.

In other words, a VS2 clarity diamond is going to look the same as a Flawless diamond to the naked eye. That's because VS-2 clarity diamonds tend to face-up eye-clean. In that case, there really isn't a need to pay more for a higher clarity. However, it's still worth including VS-1 and higher in your search. Because sometimes the cutters discount higher clarity diamonds in order to make them competitive with those of lower clarity. True story, don't overthink it.

SI2 Clarity & Lower:

As a matter of fact, I've never seen an SI-2 or lower clarity diamond that I'd call eye-clean. That's because I've always been able to see the inclusions readily and immediately without magnification. In fact, you'll read down below that we say the same thing about SI-1 clarity diamonds.

Although that may be true, you'll see a lot of references online about SI-clarity diamonds being eye-clean. And they are to some extent, but there is also a little bit of wordplay involved.

The Industry Definition of Eye-Clean:

According to the GIA Gemology course material, here's the procedure for determining whether or not a diamond is eye-clean. You're basically going to glance at the diamond from a distance of 9-12 inches. And if the inclusions are not "readily and immediately visible" then the diamond is eye-clean.

Now riddle me this, Batman. When you're buying or receiving a diamond, do you simply glance at it? The answer is obviously no, and that's where things begin to go off the rails. Because people tend to take the statement literally when diamond dealers say that a diamond is eye-clean.

When what the dealer is actually saying is that the diamond is eye-clean when viewed from 9-12 inches in the face-up position. IF you merely glance at it, but the inclusions might be visible if you scrutinize the diamond from a closer distance.

Be that as it may, I selected a stunning SI-2 clarity diamond cut by Brian Gavin for my own wedding ring. However, I did so knowing full well that I would be able to see the inclusions. Yet, the odds were that nobody else would be able to and that was true in thousands of cases.

SI-1 Clarity Diamonds:

With the aforementioned in mind, the odds are that you might be able to see an inclusion or two in SI1 clarity diamonds. At least if you're going to scrutinize the diamond closely.

Example SI1 Diamond Clarity Grade.

Example of the SI1 Diamond Clarity Grade.

Be that as it may, this range of clarity can provide great value since it tends to face-up eye-clean from 9-12 inches. In that case, it's likely to appear to be eye-clean under normal viewing conditions.

Although that may be true, it's important to note that the SI-1 clarity grade incorporates the broadest range of inclusion. In other words, the parameters for the grade are extremely broad.

Therefore, it pays to be selective when considering which SI1 clarity diamonds to purchase. Because one SI-1 clarity diamond might be more or less included than another. You can see more examples of the differences between SI-1 clarity diamonds within our article on Diamond Clarity Grading.

VS2 & VS1 Clarity Diamonds:

As a matter of fact, we suggest VS-1 and VS-2 clarity diamonds more than any others. That's because they provide great value and always seem to face-up eye-clean. In the case, VS-clarity diamonds make for great eye candy! After all, the inclusions will appear to be Very Slight under 10x magnification.

In other words, this is a fantastic grade for an engagement ring that will make it harder for your future Mother-In-Law to criticize. And we say that because there was this one who used to carry a diamond grading loupe in their purse! Seriously, we're not joking. In fact, she also used to pull the lab report for her diamond out of her purse at parties! (We can't make this stuff up, it's too good).

VVS1 & VVS2 Clarity Diamonds:

To begin with, we'll openly admit that examining a super ideal cut VVS-clarity diamond gives us goose bumps! After all, there is something magical about looking through the looking glass and burning our eyes out trying to find the inclusions. While being blinded by all the sparkle created by the virtual facets within the diamond.

On the other hand, we have to admit that we have mixed feelings about suggesting that people buy a higher clarity diamond than they might need. Because it seems too often like they're buying it while thinking that higher clarity diamonds perform better. When the reality is that it's the combination of proportions and optical precision that dictates performance.

Just Between Us Guys:

In the event that we were hanging out and you asked: "Is there any benefit to buying a VVS-1 clarity diamond?" I would probably say something like:

"Wow! Wow! Wow! Time to break in the new credit card you just got and let go of some big bucks for something you’ll never see! Get ready to burn your eyes out trying to locate the inclusions in this puppy with a 10x diamond grading loupe."

"But, seriously, VVS-clarity diamonds are Excellent for Triple A-A-Anal Engineers. You know, the ones who can’t sleep at night if the shirts in their closet aren’t all facing the same direction. On matching cedar hangers and sorted by season, collar type and color."

For the record, I just described the closets of my father and step-father. Both of whom were think-tank-engineers who were 1:99 people in their field. Obviously, that explains the manner in which I approach diamond buying for performance. As opposed to towing the party line and simply saying: "Ooooh, look! Pretty! Look how clear it is..."

Flawless & Internally Flawless Clarity:

IF & FL = Internally Flawless and Flawless = Why? Are you feeling masochistic today? What’s the point? If you can’t find the flipping inclusion in a VVS1 why go here?

“Because something in our life needs to be perfect” is the best excuse we’ve heard thus far. And hey if that works for you, it works for us. Just know that it's completely overkill and unnecessary in terms of light performance. Although that may be true, there are certain bragging rights to sporting this 2.09 carat, D-color, If-clarity, Black by Brian Gavin Diamond on your finger.

Carat Weight – It’s a Size Thing.

Legend has it that a wise woman once said that the difference between men and boys is the size of their toys! Consequently, Brian Gavin's Got Big Rocks!

Be that as it may, the odds are that your subconscious programming is telling you to buy her a 1-carat diamond. After all, you do want to (subconsciously) demonstrate your ability to provide, don't you? In the event that's true to some extent, it's also true that social pressures and influences are also at play. Although that may be true, the average online ring purchase is ±0.75 carats.

How Much Should You Spend?

Diamond Carat Weight Sizes

Visual Reference for Diamond Carat Weight.

Once upon a time, the powers that be spent a lot of money to suggest that you should spend two months salary on a ring. Lately, they've started to push the idea that three months is more appropriate. Far be it from us to tell you how much to spend on a rock, but, um, yeah, you should probably do it.

Aw, c'mon, what did you expect us to say? We are in "the diamond business" after all. But, before you actually do set out to spend three months salary on a rock. You should know that according to the Diamond Promotion Service (DPS) fewer than 30% of all the women in the world will own a one-carat diamond in their lifetime.

Under those circumstances, we wouldn't want to put you in that 30% category unless you want to go there. In that case, our recommendation is to focus on the cut quality first. After all, that is going to dictate the volume of light return and the sparkle factor. Then we would focus on the color grade and let the carat weight fall where it may.

We hope that you find this diamond buying tutorial useful and that you share it with your friends. In the event that you're searching for an engagement ring, feel free to use our Diamond Concierge Service. Our services are absolutely free for consumers and we love helping people find the right diamond.

Super Charge Your Diamond Buying Skills:

Follow the Steps in The Nice Ice® Diamond Buying Blueprint™ and Unlock the Secret for Maximizing Sparkle Factor and Light Performance. These are the Tips & Tricks from the back office of Nice Ice Diamonds.