Diamonds weighing 1.30 – 1.49 carats are extremely popular because people LOVE being able to get close to the look of a 1.50 carat diamond, without having shell out the cash demanded by the price increase which occurs between the 1.49 – 1.50 carat marks. For instance, this 1.328 carat, H-color, VS-2 clarity, diamond with medium blue fluorescence from the Brian Gavin Blue collection is a smoking hot deal compared to this 1.538 carat, H-color, VS-2 clarity, Signature Diamond from Brian Gavin which is priced $6,630.00 more primarily because it breaks the 1.50 carat mark!
Diamonds prices are based upon a relationship formula which is based upon the 4C’s of Diamond Grading [Diamond Cut Quality, Color, Clarity, Carat Weight] and price increases occur at set points of carat weight, e.g. between the 0.99 – 1.00 carat, and 1.49 – 1.50 carat, and 1.99 – 2.00 carat marks, and so on. This is a concept which people seem to grasp early on during the education process involved with buying a diamond for an engagement ring, however few people grasp the concept that diamond cut quality has a more dramatic effect upon the visual perception of diamond size than carat weight does.
One of the benefits of buying an “ideal cut diamond” cut to the center range of the specifications allocated for the zero ideal cut proportions rating as designated by the American Gemological Society Laboratory (AGSL) is that it is likely to face-up larger in diameter and produce a higher amount of light return than a diamond of equal carat weight that is cut too deep. By the same logic, a diamond cut shallower than the proportions dictated for the zero ideal cut diamond rating, is likely to face-up larger and also exhibit a lower amount of light return. In both cases, diamonds which are cut too deep, or too shallow, the primary focus by the cutter is usually upon retaining maximum carat weight, instead of producing the highest amount of light return and visual performance.
For the purposes of this example, let’s consider three diamonds:
If carat weight is your primary focus when buying a diamond, you might select the 1.50 carat, H-color, VS-2 clarity, round brilliant cut diamond from the virtual inventory of James Allen, because it is $4,830.00 cheaper than the 1.538 carat, H-color, VS-2 clarity, round brilliant ideal cut diamond from the Brian Gavin Signature collection… but this would be a Rookie Mistake.
Because this particular 1.50 carat diamond from James Allen has a total depth of 63% with a 37.0 degree crown angle which is too steep and a girdle edge which is slightly thick to very thick, and as a result the average outside diameter of the diamond is 7.19 mm and this is what the visible diameter of the diamond is. Believe it or not, the overall proportions grade of this diamond is actually AGS-1 Excellent on the AGS Proportions Scale; so the light return is likely to be pretty good, however you’re paying for a lot of carat weight that is buried in the depth of the diamond and which will not be seen from a top down profile.
The 1.538 carat diamond from Brian Gavin is a round brilliant ideal cut diamond with an average outside diameter of 7.42 mm because each section of the diamond is cut in harmony with the other sections… the total depth of the diamond is 61.7% and the table diameter is 55.7% with a crown angle measuring 34.3 degrees which is offset by a 40.9 degree pavilion angle and a thin to medium, faceted girdle and a pointed culet. Unlike the 1.50 carat diamond from James Allen, this diamond is cut to the center range of the spectrum for the AGS Ideal-0 proportions rating AND it has an overall cut grade of AGS Ideal-0 on the Platinum Light Performance grading platform, so it is verified as delivering superior light return and visual performance.
Now the 1.328 carat, H-color, VS-2 clarity, round brilliant ideal cut diamond from the Brian Gavin Blue collection has an average outside diameter of 7.08 mm, which is pretty darn close to the average outside diameter of 7.19 mm for the 1.50 carat diamond from James Allen, and it’s $1,800.00 less expensive… and it has an overall cut grade of AGS Ideal-0 on the Platinum Light Performance grading platform, so here again, we know that it exhibits a superior amount of light return and visual performance. I’m willing to bet that if you were looking across the dinner table at the two diamonds, you might not be able to tell them apart by outside diameter, but you’d probably be able to separate them by light return and sparkle factor![separator]
Seriously, who can spot a difference of 0.11 millimeters across the dinner table? But the visual difference in terms of light return and sparkle is something that people pick up on and talk about… plus the price difference of $1,800.00 goes a long way towards a nice mounting like this Halo setting from Brian Gavin
I have to admit that I’m partial to diamonds which exhibit blue fluorescence when exposed to black light or high levels of ultra-violet light because they just look cool! Fortunately diamonds with blue fluorescence tend to cost a little bit less than diamonds of equal characteristics without fluorescence, simply because of a discount which is applied to the price of diamond rough which is a remnant created by a stock investment firm in Asia during the 1980’s which attempted to distinguish itself apart from other stock investment firms by advertising that their diamond investment parcels contained no fluorescent diamonds… as other firms jumped on the no fluorescent diamonds bandwagon, it created a shorted of non-fluorescent diamonds and an overabundance of diamonds with blue fluorescence and the diamond cutters were forced to discount the price of blue fluorescent diamonds to sell them… that’s the reason for the discount, it’s stupid and it has nothing to do with the effect of blue fluorescence on a diamond. According to the GIA, blue fluorescence is little more than “an identifying characteristic” in 98% of gem quality diamonds, it has the potential to negatively impact 2% of gem quality diamonds and this is usually in the range of very strong to distinct blue fluorescence, combined with higher diamond colors such as D-E-F color.
* Diamond prices as stated by each vendor at the time this article was written, June 09, 2013 and are subject to change without notice due to fluctuations in the global diamond markets and are subject to the terms & conditions of each vendor. Refer to diamond details page for current pricing.
Todd Gray is a professional diamond buyer with 30+ years of trade experience. He loves to teach people how to buy diamonds that exhibit incredible light performance! In addition to writing for Nice Ice, Todd "ghost writes" blogs and educational content for other diamond sites. When Todd isn't chained to a desk, or consulting for the trade, he enjoys Freediving! (that's like scuba diving, but without air tanks)
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