Christie’s & Sotheby’s New York pre-auction analysis
In this pre-auction analysis, we have a relatively large amount of blue fancy color diamonds. Most of them seem to be coming from the secondhand market as almost no new blue rough have been unearthed in the last few years. As always, we will focus on visual elements and other observations that are not expressed on the GIA report nor in the catalog.
Our analysis expresses characteristics such as Undertone, Color Dispersion, and Inner-Grade (UDI; a detailed explanation appears below). We use grades 1, 2, 3, and 4 (1 being the lowest grade). The grade 4+ is granted in rare cases and stands for an exceptional characteristic. Stones that receive a minimum total UDI score of 8, without a remark, are considered to be “gems” and are probably suitable for high-end jewelry, collectors, and the investment community. A detailed explanation on our grading system is at the bottom of this article.
For your convenience we have added direct links for the GIA reports and some FCRF Rarity reports.
All images in this article review were taken with an iPhone 7 – no filters were applied.
All auction valuations are per carat and in US Dollars.
Christie’s Auction – April 17th, 2018
Lot #71
40.57 carat fancy intense yellow cushion cut, VS2
High catalog estimation: $29,579 per carat
Price Realized: $23,971 per carat
A cushion cut diamond that was cut without giving too much attention to the color dispersion and was left with a large colorless frame. The yellow undertone has no green or brown influence. The “Intense” inner-grade is above average, and the VS2 clarity grade is a result of a black crystal underneath the table facet.
Inner-Grade Color Dispersion Undertone
2 3 3
Total quality score: 8
To review the GIA Report Click here
Lot #99
2.10 carat fancy vivid blue pear cut, VS1
High catalog estimation: approximately $1,657,000 per carat
Price Realized: approximately $1,653,571 per carat
From the cutting style of this vivid blue pear shape, it is clear that the stone was polished many years ago. There is no gray undertone, and it exhibits an absolute primary blue hue. However, the color is concentrated mainly at the point and some at the rounded area of the Pear shape. The center is completely colorless and creates a very poor color dispersion. The ‘vivid’ Inner-Grade looks quite good, but one should take into consideration that the color is concentrated at two small areas of the stone, which could create the optical illusion that the Inner-Grade is high.
Inner-Grade Color Dispersion Undertone
3 2 4
Total quality score: 9
To review the GIA Report Click here
Lot #100
2.42 carat fancy vivid blue pear brilliant -cut, VS2
2.85 carat fancy intense pink pear modified brilliant cut, I1
The average High catalog estimation for both stones: $948,766 per carat
Price Realized: $856,262 per carat
This blue pear shape as well has no modifications and due to its cutting style, it would be reasonable to assume this stone had been polished a few decades ago. The color dispersion has numerous colorless areas, and the ‘Intense’ Inner-Grade is below average. The blue color has very little gray undertone and exhibits a pleasant hue.
The Pink Pear shape has a low clarity grade (I1) which is visible to the naked eye and does not meet the criteria of making the stone a “Gem”.
Vivid Blue Pear shape
Inner-Grade Color Dispersion Undertone
2 3 3
Total quality score: 8
Intense Pink Pear shape
Inner-Grade Color Dispersion Undertone
2 3 3
Total quality score: 8 (I1)
To review the GIA Reports Click here and here
Lot #167
8.42 carat fancy intense pink brilliant cut, VVS1
High catalog estimation: $712,589 per carat
Price Realized: $598,278 per carat
This 8.42 carat pink diamond was not originally polished from rough to be a cushion cut diamond, but rather a different shape. This is usually applied on round stones to improve their saturation. The low depth percentage, the large colorless areas and some remaining facets on the pavillion, indicate it was originally polished as round brilliant cut. The reason for changing the shape and the facet angling is merely to receive a stronger intensity grade. It is important to note that if the recutting from a previous shape is not done properly (in order to save some weight), the stone will suffer from a low color dispersion, as we see in this case.
The stone has an Orange fluorescence, which grants a warmer look to the hue of the diamond. A cold pink (usually referred as “Sweet”) will usually grant a premium.
Inner-Grade Color Dispersion Undertone
2 2 2
Total quality score: 6
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #208
1.27 carat fancy intense blue pear cut, VS2
High catalog estimation: $118,110 per carat
Price Realized: $548,425 per carat
This fancy intense blue pear shape exhibits a color with a fair amount of gray Undertone. The color dispersion is average, and the Inner-Grade is quite low. To an untrained eye, the Inner-Grade might look stronger due to the gray undertone.
Inner-Grade Color Dispersion Undertone
2 3 2
Total quality score: 7
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #209
2.81 carat fancy intense blue modified square brilliant cut, VVS1
High catalog estimation: $533,808 per carat
Price Realized: $773,132 per carat
This intense blue has two visual elements that need to be addressed: the first being the substantial amount of gray undertone in the hue of the stone, and the second being the fact that it has a large amount of graining, which makes the stone look a bit “oily” under a loupe. In most cases, graining lines do not affect the diamond’s appearance; however, in some cases such as this one, they do, and it might affect the price as well.
At first glance, the stone might look like a cushion shape diamond, but taking a closer look on the report, you will see that there were a few modifications to the corners which resulted in a different silhouette all together.
Inner-Grade Color Dispersion Undertone
3 3 2
Total quality score: 8 (The graining in the stone is visible)
To review the GIA Report Click here
Lot #212
3.09 carat fancy intense blue emerald cut, VS1
High catalog estimation: $970,874 per carat
Price Realized: $1,739,482 per carat
A fancy intense blue Emerald cut that was probably polished in the last century. It was cut as a regular colorless diamond with no large facets on the bottom to increase the visibility of color.
The lack of modifications in Emerald cut fancy color diamonds can result in a poor color dispersion and an overall low Inner-Grade. This can be corrected by recutting the stone; however, with the remaining 9 points, there is not much room to maneuver and create a better look. The color undertone has a low amount of gray and displays a pleasant blue color.
Inner-Grade Color Dispersion Undertone
2 1 3
Total quality score: 6
To review the GIA Report Click here
Sotheby’s Auction – April 18th, 2018
Lot #48
7.37 carat fancy intense orangy pink step cut, VS1
High catalog estimation: $678,426 per carat
Not Sold
The warm orange modifier in this large step cut stone has a quite negative impact on the overall color. From a first glimpse, one might think there is a brown modifier in the color mix, which makes it less attractive. The color dispersion is average for an Emerald fancy color diamond, and the Inner-grade is weak.
Inner-Grade Color Dispersion Undertone
2 3 2
Total quality score: 7
To review the GIA Report Click here
Lot #107
7.01 carat fancy intense pink square cut, SI2
High catalog estimation: $741,797 per carat
Not Sold
A very attractive-looking pink stone with all the needed visual elements: a high color dispersion, an attractive and “cold” pink undertone with no orange influence, and a good Inner-Grade for an Intense grade. However, in this case, the low clarity grade might be a caveat for some buyers, especially as it is visible to the naked eye.
Inner-Grade Color Dispersion Undertone
4 3 4
Total quality score: 11 (Low clarity SI2)
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #113
20.81 carat fancy intense yellow cushion cut, VVS2
High catalog estimation: $24,027 per carat
Price Realized: $22,633 per carat
This large Fancy intense yellow cushion cut diamond exhibits a strong Inner-Grade for an Intense, which borderlines to a vivid yellow. The color dispersion is quite good, with some colorless patches around the stone. The yellow hue has no green or brown undertone.
Inner-Grade Color Dispersion Undertone
4 3 4
Total quality score: 11
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #138
3.47 carat fancy intense blue step cut, I1
High catalog estimation: $720,461 per carat
Price Realized: $1,920,259 per carat
Other than its low clarity grade – caused by a large hole next to one of the corners, visible to the naked eye – the stone has some very good characteristics. The Inner-Grade is very strong, and the undertone has no gray influence, which results a very pleasant blue hue.
The color dispersion, on the other hand, is below average due to the very low depth percentage, but it gives the stone a much larger face-up look in comparison to its actual weight.
Inner-Grade Color Dispersion Undertone
4 2 4
Total quality score: 10 (I1)
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
General
We use 1, 2, 3, 4, and 4+ to grade the three visual elements that GIA is silent about, that, however, impact value dramatically.
Inner-Grade refers to the strength of color within each GIA saturation category:
Grade 1 weakest, bordering the saturation below.
Grade 2 weak (most abounded).
Grade 3 full-bodied color (above average).
Grade 4 very strong saturation.
Grade 4+ applies for the vivid category only, exhibiting the strongest possible saturation (rarely seen).
Undertone refers to a subtle hue influence in the body color of the stone. For example:
A fancy blue diamond with a significant gray presence in its general appearance will be graded with a low undertone grade of 1. A fancy blue that has no gray influence and will be close to a primary blue will receive the grade 4.
In a pink fancy color diamond, a stone with a warm undertone (such as orange or brown) will receive a low undertone grade. A pink stone with a cold undertone (such as purple) will receive a high grade.
In yellow fancy color diamonds, low foreign influence or a light orange influence will grant the stone a high undertone grade. When the yellow undertone looks like a true primary yellow, it will receive the rare grade 4+. Green and brown undertones will grant a low grade in the yellow category.
Color Dispersion relates to how well the color is dispersed in the face-up view of a fancy color diamond, regardless whether the GIA grades the stone as even. A stone with many colorless areas will receive the grade 1, while a stone that exhibits its face-up view with no colorless patches will receive the grade 4+. Unlike the first two elements, color dispersion is not a gemological quality and has only to do with cutter proficiency.
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