One Minute Diamond Buying Guide

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This diamond buying guide contains everything you need to know to buy a spectacular-looking ideal cut diamond online, and it only takes a few minutes to read.

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

The minimum selection criteria that we recommend for round ideal cut diamonds are as follows: An overall cut grade of AGS Ideal with proportions within the range below. You should also ensure that the diamond exhibits a higher degree of optical precision.

That is the consistency of facet shape, size, and alignment from the perspective of 360-degrees. Consequently, the labs do not account for optical precision. In that case, you'll need to judge it for yourself using a Hearts and Arrows Scope.

Diamond Buying Guide Blue Nile Petite Floral Halo.

Petite Floral Halo by Blue Nile Diamonds.

Diamond and Jewelry Coupons & Sales:

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The AGS/GIA Proportions Range Is Too Broad.

Tapered Baguette Engagement Ring Round Diamond Buying Guide

3-Stone Engagement Rings by Brian Gavin.

The range of proportions relied upon by the AGS and GIA are broader than we recommend in this diamond buying guide. Under those conditions, there are a lot of ideal cut diamonds that 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 ratio of white and colorful sparkle will virtually be the same. 

This Brian Gavin Signature diamond looks terrific because the proportions are within the following range:

  • 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 size: AGS pointed or GIA none.

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 an I-color diamond for my 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 look warmer compared to diamonds in the D-F colorless and G-I near-colorless range.

K-color Brian Gavin diamond.

K-color Brian Gavin Signature Diamond.

The diamond will still face-up white when set in white gold or platinum prongs. That's because the white metal color 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.

Our eyes tend to look towards the center stone's larger surface area. Under those circumstances, it is more difficult to ascertain the difference in body color. In that case, this diamond buying guide recommends a range of D-K color depending on your preference and sensitivity.

Diamond Color by Temperature:

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. At the same time, other people might choose 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. 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. The latter of which is subjective mainly because the lighting temperature will affect your perception of diamond color.

Diamond Buying Guide for Blue Fluorescence:

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.  The center stone in Brian Gavin's wife's wedding set is a Brian Gavin Blue fluorescent diamond.

Our trade status provides us with access to everything. We choose diamonds with blue fluorescence 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 love the way that blue fluorescent 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.

Example SI1 Diamond Clarity Grade Brian Gavin Signature Diamond.

Example of SI1 Clarity Diamond from Brian Gavin.

SI-1 clarity diamonds may seem to be eye-clean. However, the industry standard for making this determination is merely glancing at the diamond from a distance of 9-12 inches.

The industry will label the diamond eye-clean if the inclusions are not readily and immediately visible to the 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 may be preferable if you can't sleep at night unless all the shoes in your closet face the same direction. If you also organize your shirts by color, collar type, and style, this diamond buying guide recommends you buy VVS-2+ clarity diamonds.

Going Beyond the Basics:

Bella Vaughan for Blue Nile Roma diamond engagement ring

Bella Vaughan for Blue Nile Oval-shaped Diamond.

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.

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.

If you're interested in shapes other than round, be sure to check out our guides for fancy shape diamonds. Needless to say that we have a diamond buying guide for the most popular diamond shapes. We also know the best places to buy diamonds online and provide in-depth reviews.

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.

Black by Brian Gavin Diamond 1.79 carats, E-color, VS-1 clarity.

Black by Brian Gavin Diamonds Performance+

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! Nobody cuts diamonds like Brian Gavin. After all, he holds the patent for maximizing light performance in the modern round brilliant. Consequently, the proportions of his diamonds are within the range we recommend in this diamond buying guide.

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 is 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 & Symmetry. 
** 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.

Tension Set Engagement Ring from Brian Gavin.

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. Also, a crown angle steeper than 35.5° is likely to make round diamonds look dark.

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, this type of obstruction makes diamonds look dull and dark.

Pavilion Angle:
White Gold Infinity Pave Setting by James Allen.

White Gold Infinity Pave Setting by James Allen.

The pavilion is the lower half of the diamond below the girdle edge. Consequently, I recommend a narrow range of pavilion angle 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 a good volume of 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:
Black by Brian Gavin Arrows.

Black by Brian Gavin Diamond Arrows Pattern.

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

Round brilliant cut diamonds with lower girdle facets in the 80-82% range tend to produce pin-fire type sparkle. That means that the sparkle factor is likely to be smaller and less intense.

The pin-fire type sparkle problem is that our human eyes have difficulty dispersing smaller white light flashes into colored light/sparkle.

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

Beware of Rounding Off:

In that case, you'll need to determine the actual lower girdle facet length by visual estimation. Consequently, you might be aware of the gap between the ranges of 75 – 78% and 80 – 82%.

Specifically, where 79% should be on the scale of preference. 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 good middle ground. Of course, that depends on whether you know the type of sparkle you prefer.

James Allen Diamond Buying Guide Cushion Outline Setting.

Cushion Outline Pave Gallery by James Allen.

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 most likely to mimic the effects of firelight. Of course, we don't live under those lighting conditions in this modern age.

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%.

Besides, I also prefer the look of the arrows pattern that creates. In contrast, 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 hearts' shoulders or lobes 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 star facets' length is affected by the size of the table facet and the crown angle.

Black by Brian Gavin Diamond Prices.

Black by Brian Gavin H&A Diamond.

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

If the hearts' pattern is consistent, the exact star facet measurements are not critical. If the hearts' are irregular and the degree of obstruction is prominent, you should buy a different diamond.

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

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.