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Annual March Diamond Madness - Meet Our Champion - Up to 11% Off
Annual March Diamond Madness - Meet Our Champion - Up to 11% Off
Who has the best diamond prices online?

Who has the best diamond prices online?

Price is a factor whenever we buy pretty much anything, and we all obviously want to get the best price when buying luxury items such as diamonds online, however do you know how to distinguish the difference between a high quality diamond being sold for a fair price; and one which has similar characteristics that is selling for less, but only because the cut quality is actually inferior?

The reality is that most internet diamond dealers are working off of minimal profit margins, which enable them to compete globally instead of locally as most traditional jewelry stores try to do… thus when one vendor seems to be offering significantly better prices than their competitors for diamonds which seem similar, the odds are that the price difference is due to a difference in the overall cut grade of GIA Excellent and AGS Ideal.

GIA Excellent vs AGS Ideal Cut diamonds:

One of the first concepts that trip up a lot of diamond buyers is the belief that the parameters for the GIA Excellent cut grade are equivalent to the AGS Ideal-0 classification, and nothing could be further from the truth!

While the criteria used to determine the Polish and (meet point) Symmetry is pretty much the same for diamonds graded by the GIA and those graded by the American Gem Society Laboratory (AGSL), the parameters for the GIA Excellent proportions grade are much broader than the range designated by the AGS Laboratory for their zero ideal cut proportions rating.

The Light Performance based grading platform offered by the AGSL relies on Angular Spectrum Evaluation Technology (ASET) to evaluate diamonds for Brightness, Fire, Leakage and Contrast, which are essential characteristics to consider when evaluating ideal cut diamonds. The ASET image for this 0.922 carat, G-color, VS-2 clarity, Brian Gavin Signature diamond, appears on the diamond grading report to the left.

The color red is used to represent the brightest light which enters the diamond and which is being reflected back towards the observer; the color green represents the second brightest light; and the color blue is used to indicate contrast; all of this is explained in detail in our diamond grading tutorial on visible perfection.

In addition to evaluating diamonds for brightness, fire, leakage, and contrast, the Light Performance grading platform offered by the American Gem Society Laboratory takes five practical elements of diamond design into account: weight ratio, durability, tilt, girdle durability, culet size.

The first element, weight ratio, is a factor of diamond valuation that is largely overlooked by consumers, simply because they don’t know what to look for… In essence it is the practice of cutting diamonds so that they achieve a high level of visual performance, without leaving excess weight within the body of the diamond. The fact that the AGS grading platform takes this factor into account, is another primary difference between the GIA Excellent and AGS Ideal cut grades.

Differences in how the AGS & GIA measure lower facet length:

Another little known difference between the GIA and the AGS gemological laboratories is how they measure the lower girdle facet length, because the AGS bases their measurement based on the height of the lower girdle facets, while the GIA uses the radius of the facets to determine the length. This can cause confusion because the two methods of measuring the lower girdle facets produces different results, for instance a 75% lower girdle measurement on an AGS diamond grading report, is likely to be more like 73% the way the GIA calculates it; while a lower girdle facet length of 80% on a GIA diamond grading report, would be more like 81.5% if measured by the AGS.

Why should something like this concern you? Because the length of the lower girdle facets has a direct impact upon the size of the flashes of light that are commonly referred to as sparkle! Which method of measuring the lower girdle facets is correct? We think that the method used by the AGSL makes the most sense; the only reason the GIA still measures it the other way is because it enables their students to estimate the length of the lower girdle facets by using a table gauge.

I can respect the concept behind providing gemological students with a reliable method for estimating the length of the lower girdle facets using what is the gemological equivalent of a slide rule, but at this level of the game, we use Sarin DiaMension computerized proportions analysis to determine the proportions of diamonds, some companies use OGI or Helium machines, the concept is the same.

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