The One Minute Diamond Buying Guide:

This diamond buying guide contains everything you need to know to buy a round ideal cut diamond online.

And it only takes about a minute to read. So, Get Ready. Set. Go!

This is the minimum selection criteria that we recommend for round brilliant cut diamonds:

  1. 1
    Overall Cut Grade of AGS Ideal or GIA Excellent.
  2. 2
    AGS Ideal  Proportions (see below).
  3. 3
    AGS Ideal or GIA Excellent Polish.
  4. 4
    AGS Ideal or GIA Excellent Symmetry.

The AGS/GIA Proportions Range Is Too Broad.

As a matter of fact, the range of proportions relied upon by the AGS and GIA are too broad. Under those conditions, there are a lot of ideal cut diamonds that really don't perform well.

Consequently, the range of proportions we recommend in this diamond buying guide is very tight. Be that as it may, it also produces the highest volume of light return. At the same time, it also produces a virtual balance of brilliance and dispersion. That means that the balance of white and colorful sparkle will virtually be the same.

  • Total depth between 59 – 61.8%*
  • Table diameter between 53 – 58%
  • Crown angle between 34.3 – 35.0 degrees**
  • Pavilion angle between 40.6 – 40.9 degrees
  • Lower girdle facets between 75 – 78%***
  • Star facets between 45 – 50%****
  • Girdle thickness between thin and slightly thick.
  • Culet: AGS pointed or GIA none.

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Diamond Buying Guide on Color Grades:

The spectrum between D-color and G-color will face-up  bright white.

Diamonds in the H-color and I-color range will look white to most people. That is why I selected and I-color diamond for my own wedding ring. 

Most people begin to detect a hint of color more easily in diamonds that are J-color and lower. In other words, diamonds that are L/M/N and lower tend to look warmer. As compared with diamonds in the D-F colorless and G-I near-colorless range.

K-color Brian Gavin diamond.

The diamond will still face up white when set in white gold or platinum prongs. That's because the color of the white metal touching the edge of the diamond will reflect throughout the stone.

That is why this K-color Brian Gavin signature diamond faces up white in this Anita Halo setting by Brian Gavin in 18 K white gold.   By the way, the accent diamonds set in the ring are F-G-color.

As a matter of fact, our eyes tend to be drawn to the larger surface area of the center stone. Under those circumstances, it is more difficult to ascertain the difference in body color.

Diamond Color by Temperature:

As a matter of fact, it might be easier to think of diamond color in terms of temperature. After all, some people are likely to prefer diamonds that are cooler in appearance. While other people might prefer diamonds that are warmer in hue and saturation.

James Allen Ring Reviews 17110Y14

Sleek Diamond Engagement Ring by James Allen.

Be that as it may, the color grade has virtually no effect on light performance. In that case, diamond color is strictly a matter of personal preference. In other words, one color grade does not necessarily look better than another.

However, the perception of diamond color might affect your decision to choose one color over another. In that case, you might consider how diamonds of different colors look against your skin tone.

Of course, the appearance of your diamond is going to change depending on the environment. As a matter of fact, the diamond in this sleek engagement ring from James Allen looks very bright. However, that has more to do with the cut quality than the color grade. One thing we can't cover in a diamond buying guide is how lighting temperature will affect your perception.

Diamond Buying Guide for Blue Fluorescence:

As a matter of fact, blue fluorescent diamonds are very popular with our clients. That's because they can face-up whiter and brighter than non-fluorescent diamonds.

Brian Gavin Blue Diamond Buying Guide

Brian Gavin Blue Fluorescent Diamonds.

Practically every diamond that I've chosen for myself has exhibited medium to strong blue fluorescence.  In addition, the center stone in Brian Gavin's wife's wedding set is a Brian Gavin Blue florescent diamond.

It goes without saying that our trade status provides us with access to everything. The reason why we choose diamonds with blue fluorescence is because it tends to make diamonds look even whiter and brighter.

From my perspective, blue fluorescence is like nature's whitewash for diamonds. Under those circumstances, it's kind of like a blue filter for photography. Plus, I just love the way that blue florescent diamonds glow neon blue under blacklight. As a result, this diamond buying guide gives blue fluorescent diamonds two thumbs up!

Diamond Buying Guide for Clarity:

The VS-2 diamond clarity grade delivers the biggest bang for the buck.  In the first place, diamonds that are VS-2  in clarity face-up eye clean. In that case, they look the same as higher clarity diamonds without magnification.

VS-1 clarity diamonds are a good option if you want the inclusions to be more difficult to locate using 10x and higher magnification.

SI-1 clarity diamonds may be deemed to be eye clean. However, the industry standard for making this determination is to simply glance at the diamond from a distance. of 9-12 inches.The diamond is considered to be eye clean if the inclusions are not readily and immediately visible to trained diamond grader from that distance. However, this is not how people tend to scrutinize their diamonds upon receipt.

Consider diamonds in the SI-1 clarity range if you’re trying to get the biggest bang for your buck. As long as you don’t mind being able to see an inclusion or two without magnification.

VVS-2 and higher clarity diamonds contain inclusions that will be difficult to locate using 10x diamond grading magnification. Higher clarity diamonds are good if you can’t sleep at night unless all the shoes in your closet are facing the same direction. In that case, your shirts are probably arranged by type on matching hangers that are also facing the same direction.

Don’t accept a diamond graded by any other laboratory other than the AGS, GIA, or HRD. The latter of which is the diamond grading laboratory for the Belgium High Diamond Council.

Going Beyond the Basics:

Now you know all the details necessary to buy a stunning looking diamond. However, I'm willing to bet that you want to know more. That is why the following section expands on the recommendations within this diamond buying guide.

 Why Adhere To Such A Strict Range of Diamond Proportions?

The range of proportions outlined above will produce the highest volume of light return and a virtual balance of brilliance and dispersion. It represents the center range or "Target Zone" of the AGS Ideal and GIA Excellent Grade.

They like to say that there's an ideal cut diamond for every preference. That might explain why the range of proportions for the AGS Ideal and GIA Excellent cut grades are so broad.

I suppose that one could argue that high levels of light return and performance are possible within a broad-spectrum of proportions.  However, I find that the proportions outlined above are more likely to produce the look that I prefer.

Of course, I'm referring to something like this Black by Brian Gavin Diamond. Needless to say, that it's cut like a dream! As a matter of fact, nobody cuts diamonds like Brian Gavin. That's because he holds the patent for maximizing light performance in the modern round brilliant.

Diamonds with proportions outside my preferred range are more likely to exhibit:

* Table Diameter:

In the first place, the total depth of a diamond does not necessarily have a bearing on light return. Especially if the crown and pavilion angle offset are within the correct range. Under those circumstances, the total depth measurement can be higher. For example, we wouldn't think twice about something like this: 

  • 62% Total Depth.
  • 56% Table diameter
  • 34.5 degree Crown angle.
  • 40.8 degree Pavilion angle.
  • Medium to slightly thick, faceted girdle.
  • Pointed culet.
  • Excellent Polish.
  • Excellent Symmetry.

Provided of course that the ASET Scope image meets our expectations. In other words, the ASET isn't showing signs of leakage and light is reflecting evenly. As a matter of fact, the Black by Brian Gavin diamond in my son's engagement ring has a 62% total depth. As stated previously, it's a non-issue because the critical angles are spot-on.

** Crown Angle:

In the first place, the crown is the top portion of the diamond above the girdle edge. A crown angle between 34.3 to 35.0° tends to produce a virtual balance of. brilliance (white sparkle) and dispersion (colored sparkle/fire). Any variance from this range is likely to affect the balance of brilliance and dispersion.

Diamond Buying Guide Tension Settings.

Stephen Kretchmer Tension Setting.

For example, a crown angle less than 34° is likely to produce more brilliance. However, it will probably be at the expense of dispersion.  Diamonds with shallow crown angles are also more likely to exhibit obstruction under the table facet.

A crown angle steeper than 35.5° is likely to produce more dispersion in a round brilliant cut diamond. However, it will be at the expense of brilliance. In addition, a crown angle steeper than 35.5° is likely to make round brilliant cut diamonds look dark in the middle.

As a matter of fact, variances in the crown angle and optical precision are the primary cause of obstruction. Those are the black asymmetrical shapes adjacent to the arrow shafts. Consequently, obstruction makes diamonds look dull and dark.

Pavilion Angle:

To begin with, the pavilion is the lower half of the diamond below the girdle edge. As a matter of fact, the range of pavilion angle that I recommend is quite narrow. That's because it's most likely to produce the highest volume of light return. A pavilion angle lower than 40.5° in a round brilliant cut diamond produces a reflection that looks flat. Just think of the way that light reflects off a shallow fishpond and you've got the picture.

A pavilion angle steeper than 41.0° is not likely to produce good light return. Especially if the pavilion depth is 43.5% which happens to be "the critical tipping point" where light begins not to reflect fully off the pavilion facets.

*** Lower Girdle Facet length:

I recommend a Lower Girdle Facet (LGF) length between 75 – 78% because that tends to produce broad-spectrum sparkle. That means that the sparkle will be larger in size, bolder, brighter, and more vivid.

Round brilliant cut diamonds with lower girdle facets in the range of 80-82% tend to produce pin-fire type sparkle. That means that the sparkle factor is likely to be smaller and less intense. The problem with pin-fire type sparkle is that our human eyes have difficulty dispersing smaller flashes of white light into colored light / sparkle.

Under those conditions, pin-fire type sparkle is likely to seem more brilliant (white sparkle). However, it is also likely that you will see less dispersion (colored sparkle/fire).

Beware of Rounding:

As a general rule, the GIA rounds-off several measurements on the lab report. For example, a lower girdle facet length of 78% will be rounded off to 80%. In that case, you'll need to determine the actual lower girdle facet length by visual estimation.

Consequently, you might be aware of the a gap between the ranges of 75 – 78% and 80 – 82%. Specifically, the one where 79% should be on the scale of preference. As a matter of fact, I consider that to be the critical tipping point where the type of sparkle might go either way. Depending on your viewpoint, that might make it seem like a good middle ground. Of course, that depends on whether you know the type of sparkle you prefer.

Be that as it may, I can tell you that pin-fire sparkle tends to look best under jewelry store halogen lighting. After all, that is a lighting environment that is designed to mimic the effects of firelight. Of course, we don't live under those lighting conditions in this modern age.

As a matter of fact, we live and work under diffused lighting for the most part. In that case, diamonds that exhibit broad-spectrum sparkle tend to look best. Under those circumstances, I tend to focus on diamonds with an LGF between 75 - 78%. In addition, I also prefer the look of the arrows pattern that creates. Whereas the arrows pattern that results from an LGF of 80% tends to look thinner and more spindle-like.

**** Star Facet Length:

Star facets are the small triangular shaped facets located on the crown section of the diamond. They appear between the kite shaped bezel facets and border the edge of the table facet.

Star facets serve to round off the shoulders or lobes of the hearts in super ideal round brilliant cut diamonds.

The optimum star facet length is between 45 – 55% which will create nice rounded shoulders on the hearts. However, it is acceptable for the star facets to be between 40 – 58%. The length of the star facets is affected by the size of the table facet and the crown angle.

It's important to understand that the star facets are considered to be a minor facet group. While people tend to get caught up on specific measurements, I suggest simply focusing on the images.

If the hearts pattern is formed consistently, the exact star facet measurements are not important. If the hearts are irregular and there is heavy obstruction, then I’d suggest a different diamond.

Consequently, the 5 Minute Version of Diamond Buying Success expands on the concepts herein. Obviously, we hope that you found this diamond buying guide insightful. Let us know if we can help you find the diamond of your dreams.

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Copyright 2020 by Gray Matter Development LLC

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