Sotheby’s Hong Kong pre-auction analysis
This pre-auction analysis 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 total UDI score of 8 or above (SI1 or better) 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 the 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.
Lot #1776
14.18 carat fancy blue step-cut, VVS2
High catalog estimation: $540,931 per carat
Not sold
A rare and important size and shape for any blue diamond, however in spite of the closed mounting on the back and the pink halo, the overall “blue experience” is quite saddled, especially due to the low color dispersion on the face up.
The color dispersion is low, with many colorless areas, and receives a grade of 2.
The inner-grade receives a grade of 3. However, in this particular case it would be wise to see the diamond out of the mounting to determine its real inner-grade.
The blue undertone is quite good and receives a grade of 3.
Total quality score: 8
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #1658
1.26 carat fancy intense blue step cut, IF
1.15 carat fancy intense pink, IF
High catalog estimation: $636,548 per carat
Not sold
Interesting “Toi et Moi” ring with two emerald cut diamonds. The difference in weight between the two is compensated by a low depth of 50% on the pink.
The Pink:
The color dispersion is below average for a fancy color emerald cut and receives a grade of 2.
The inner-grade is strong and receives a grade of 4.
The undertone of the pink is “cold” and receives a grade of 3.
Total quality score for the pink: 9
The Blue:
The color dispersion receives a grade of 3.
The inner-grade is strong and receives a grade of 4.
The undertone exhibits some noticeable amount of gray and receives a grade of 2.
Total quality score for the blue: 9
To review the GIA Reports Click here (Blue) and here (Pink)
Lot #1650
7.77 carat fancy vivid yellow step cut, VVS2
High catalog estimation: $57,586 per carat
Not sold
Whoever polished this diamond went out of his way to come up with as many 7s as possible, including a matching depth percentage of 70.07% (to match the 7.77 carats of course). Looking at the GIA report, one can assume that the stone could have been easily polished into an internally flawless with a minimum weight loss, however the special (lucky number) weight would have been lost.
The color dispersion is above average and receives a grade of 3.
The inner-grade receives a grade of 3.
The yellow undertone is pleasant to the eye and receives a grade of 3.
Total quality score: 9
To review the GIA Report Click here
Lot #1632
1.08 carat fancy deep bluish green step cut, SI2
High catalog estimation: $378,785 per carat
Not sold
Although in this case the stone receives a high total quality score, due to the low clarity grade and the fair symmetry, it doesn’t qualify to be a “gem” (unless it goes through a re-cut procedure) .
The color dispersion receives a grade of 4.
The inner-grade receives a grade of 4.
The undertone receives a grade of 3.
Total quality score: 11 (SI2)
To review the GIA Report Click here
Lot #1639
6.40 carat fancy orangy pink pear, IF
High catalog estimation: $219,725 per carat
Price Realized: $169,615 per carat
According to the GIA color description, the color composition in this stone is mostly pink, with 15%–25% orange modifier, which gives it a very warm color. As a result it receives a low color grade for the undertone, 2.
The color dispersion receives a grade of 3 with some noticeable colorless areas on both sides.
The inner-grade is solid and receives a grade of 3.
Total quality score: 8
To review the GIA Report Click here
Lot #1643
6.32 carat fancy vivid yellow old European cut, VVS1
High catalog estimation: $70,797 per carat
Price Realized: $55,440 per carat
In cases of a branded piece of jewelry it is important to verify its authenticity. Especially in cases where you have a diamond with fair symmetry (in this case, not a typical Tiffany and Co diamond during the year 2012 – the date of the GIA report). In these cases it is recommended to buy the stone as is, without granting a special premium to the fact the diamond is branded.
The color dispersion is quite high for an old European round brilliant and receives a grade of 3.
The inner-grade is a bit low and receives a grade of 2.
The yellow undertone receives a grade of 3.
Total quality score: 8
To review the GIA Report Click here
Lot #1611
10.49 carat fancy vivid yellow step cut, IF
High catalog estimation: $85,308 per carat
Not sold
Although there are significant colorless areas, we look at Emerald cut diamonds in comparison to other step cut diamonds and grade the color dispersion in this case 3.
The inner-grade is quite solid and receives a grade of 3.
The undertone receives a grade of 3 as well.
Total quality score: 9
To review the GIA Report Click here
Lot #1618
15.69 carat fancy vivid yellow cut-cornered rectangular modified brilliant, IF
High catalog estimation: $48,887 per carat
Price Realized: $55,544 per carat
The color dispersion is low with a noticeable colorless frame and receives a grade of 2.
The inner-grade is above average and receives a grade of 3.
The undertone receives a grade of 3 as well.
Total quality score: 8
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #1621
7.28 carat fancy vivid yellow oval, VVS1
High catalog estimation: $114,143 per carat
Not sold
This diamond is cut as a colorless diamond with no modifications in the facet alignment and looks like it was polished a while ago.
The color dispersion is low and receives a grade of 2.
The inner-grade is above average and receives a grade of 3.
The yellow undertone receives a grade of 3 as well.
Total quality score: 8
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #1645
10.30 carat fancy vivid orangy yellow square emerald cut, IF
High catalog estimation: $136,528 per carat
Price Realized: $135,079 per carat
The color dispersion is above average in comparison to most step cut diamonds and receives a grade of 3.
The above average inner-grade receives a grade of 3.
The undertone receives a grade of 3.
Total quality score: 9
To review the GIA Report Click here
Lot #1659
30.16 carat fancy vivid yellow cut-cornered rectangular step cut, VS1
High catalog estimation: $105,968 per carat
Price Realized: $94,290 per carat
An important size for a vivid yellow modified step cut.
The stone is an Emerald-cut look-alike polished with significant modifications in order to bring out the color, which created a relatively high color dispersion and receives a grade of 3. Having said that, without this modification it would have probably been graded as an intense yellow.
The vivid inner-grade is below average and receives a grade of 2.
The yellow undertone doesn’t have a significant green or brown undertone and receives a grade of 3.
Total quality score: 8
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #1761
4.18 & 4.04 carats fancy intense yellow cut-cornered rectangular modified brilliant, VS2
High catalog estimation: $17,050 per carat
Price Realized: $17,437 per carat
Both stones:
The color dispersion is high and receives a grade of 4.
The inner-grade receives a grade of 3.
The yellow undertone receives a grade of 3.
Total quality score: 10
To review the GIA Report Click here (4.18ct) and here (4.04ct)
Lot #1762
5.29 carat fancy vivid yellow step-cut, VS1
High catalog estimation: $144,998 per carat
Price Realized: $124,279 per carat
The color dispersion is low. It has large colorless areas, even for an Emerald cut, and receives a grade of 2.
The inner-grade is quite strong and receives a grade of 3.
The yellow undertone receives a grade of 3.
Total quality score: 8
To review the GIA Report Click here
To review the FCRF Rarity Report Click here
Lot #1782
5.01 carat fancy vivid purplish pink cushion
High catalog estimation: $510,339 per carat
Price Realized: $491,330 per carat
A pink diamond with very attractive characteristics, but doesn’t meet the threshold for being a “Gem” due to its poor (and visible to the eye) clarity.
The color dispersion receives a grade of 4.
The inner-grade receives a grade of 3.
The yellow undertone receives a grade of 3.
Total quality score: 10 (eye visible SI2)
To review the GIA 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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