Pre-Auction Analysis: October 3rd 2018, Sotheby’s Hong Kong, Magnificent Jewels

Our Pre-Auction analysis focuses on elements that are hidden from the unprofessional eye and as always, we will describe the important visual elements for those who cannot attend the preview. We will discuss characteristics such as Undertone, Color Dispersion, and Inner-Grade (UDI; a detailed explanation appears at the bottom of this article).

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 mostly suitable for high-end jewelry, collectors and the investment community. For your convenience we have added direct links for the GIA reports.

• All images in this article review were taken with an iPhone 10, no filters were applied.
• All auction valuations are per carat and in US Dollars.

Lot #1892

5.00 carat fancy vivid blue Emerald Cut, VS2

High catalog estimation: $3,057,600 per carat

The ultimate test for a ‘Vivid’ is whether you recognize its lively and lucid detailed colorful nature, without doubting if it’s actually vivid or not or look at the GIA report for reassurance.
In this case, a second look at the report is definitely needed. This blue diamond is saturated to the point that it loses its translucency and livelihood and could appear like a classic fancy ‘Deep’ blue, rather than a ‘Vivid’.
If a buyer is actually considering wearing the stone and not only consider it as an investment, he needs to view it under all lighting conditions prior to taking this decision.
Unfortunately, our blue diamonds’ grading system doesn’t really refer to translucency levels but rather to the undertone of the color (i.e. the amount of ‘gray’ in the hue), thus, the remark below the chart should have considerable impact despite the high quality score.

Total quality score: 11 – low translucency which does not correspond to the ‘Vivid’ grade.

To review the GIA Report Click here (2135360540)

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Lot #1858

A total of 8 fancy vivid yellow round brilliant cut diamonds

8.43ct, 8.36ct, 7.50ct, 7.21ct, 5.42ct, 5.10ct, 4.62ct, 4.53ct All vivid yellow old European brilliant cut. Clarity: IF to VS2

High catalog estimation: $119,507 per carat

A rare collection of old European brilliant cut diamonds. In cases where one finds a substantial amount of matching antique fancy color diamonds, the value will derive from the ‘Ensemble’ and not so much from the gemological characteristics. Looking at the high depth percentage, small table and open cutlets, it will be safe to say that these round diamonds were genuinely planed and polished during the beginning of the last century. Having said that, from the high clarity of this batch, the lack of chips and bruises, we can assume that they went through a “cosmetic” polishing treatment to remove the marks of history, and obviously placed in a new mounting. The grades in the charts represent the average score.

Total quality score: 8

To review the GIA Report Click here  (1172305107)

To review the GIA Report Click here  (6173266814)

To review the GIA Report Click here  (2175305111)

To review the GIA Report Click here  (1176305114)

To review the GIA Report Click here  (5172305126)

To review the GIA Report Click here  (2175305121)

To review the GIA Report Click here  (5172305131)

To review the GIA Report Click here  (5172305134)

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Lot #1857

3.64 carat fancy pink round brilliant, IF

High catalog estimation: $490,000 per carat

Round fancy color diamonds that have the greatest premium among all shapes. The reason for that lies in the fact that there are very few things a cutter can perform in order to concentrate the color, thus new round fancy color diamonds are rarely seen at the market place, as the tendency will be to polish fancy shapes instead. Alongside this notion, round fancy color diamonds, graded as ‘Fancy’, or lower, are still rare but create a poor visual impact, and end up being less desirable by the end client.
This 3.64 fancy pink is misrepresented in the auction catalog. In reality, it exhibits a low inner-grade and low color dispersion.

Total quality score: 7

To review the GIA Report Click here  (1162587333)

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Lot #1856

3.47 carat fancy intense blue pear shape, VS1

High catalog estimation: $1,028,012 per carat

A fancy intense blue pear-shape diamond, cut as a wide colorless brilliant cut, a cutting style indicating that it was polished during the end of the last century. Applying the colorless polishing doctoring on fancy color diamonds creates many colorless patches, and does not realize the full potential of the color. As clearly seen in the picture, the blue color located mostly at the point of the pear shape, leaving most of the stone quite pail. The blue undertone exhibits a noticeable gray undertone and receives a low grade.

Total quality score: 6

To review the GIA Report Click here  (6193504643)

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Lot #1854

11.87 carat fancy vivid yellow pear shape, IF

High catalog estimation: $160,994 per carat

A large pear-shape with a very strong vivid inner-grade. As opposed to the catalogue image there are some noticeable colorless areas around the stone. The lozenge shaped window in the culet for example, results from the same colorless areas in the crown reflecting back to the culet.

Total quality score: 10

To review the GIA Report Click here  (2185742143)

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Lot #1847

6.27 carat fancy yellow pear shape, IF

5.86 carat fancy yellow pear shape, VS2

High catalog estimation: $18,476 per carat

Two fancy yellow pear shapes joined together to create a pair of earrings. Looking at the two different GIA dates of issue, the different faceting alignment, different table size and the fact that only one has a laser inscription, we might assume that the stones were matched spontaneously and were not cut to match. This fact doesn’t really have an effect on the value of the stones but could cause some discomfort to the experienced buyer.  

Total quality score: 9

To review the GIA Report Click here  (1172365557)

To review the GIA Report Click here  (2173473518)

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Lot #1840

0.87 carat fancy blue brilliant shape, SI1

High catalog estimation: $95,184 per carat

A fancy blue diamond with 70% table and 56% depth which proportions are a bit unusual for a round brilliant. These odd proportions apply some negative effect on the color dispersion.

Total quality score: 8

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Lot #1751

4.31 carat fancy intense purplish pink cut-cornered square modified brilliant-cut

High catalog estimation: $295,592 per carat

A pleasant looking pink Radiant cut with a ‘color only’ report. The stone is heavily included and visible to the naked eye. If it would have been with a full report it would have probably be graded as an I1clarity. When we placed the stone under a UV light it seems to have a ‘Strong blue fluorescence as well.
The stone has a very good undertone exhibiting a desirable “cold” (sweet) pink and very few colorless patches.

Total quality score: 10 – color only report

To review the GIA Report Click here  (2183082670)

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Lot #1749

1.42 carat fancy intense blue radiant, IF

High catalog estimation: $538,310 per carat

A fancy intense blue radiant with no gray undertone, exhibiting a primery blue hue. The stone has a medium size colorless frame around the table and a solid Inner-Grade.

Total quality score: 10

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Lot #1750

1.91 carat fancy green rectangular modified brilliant shape, VS2

1.68 carat fancy green cut-cornered rectangular modified brilliant-cut, SI1

High catalog estimation: $ 113,560 per carat

Although some gemological parameters don’t completely match, it is quite rare to find two compatible ‘Fancy Green’ diamonds that create a pair of earrings. The inner-Grade comes across as strong for both stones and with a few colorless areas. The ‘Undertone’ does not match perfectly but due to the fact that this is such a rare color, a more forgiving approach may be adopted in this case.

1.91

Total quality score: 11

1.68

Total quality score: 12

To review the GIA Report Click here  (1172324973)

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Lot #1748

1.38 carat fancy vivid bluish green cushion shape, SI1

High catalog estimation: $664,696 per carat

A rare diamond hue exhibiting a green body color with a minor percentage of blue in the color mix. In some cases the result of this color occurs when a diamond that contains Boron is exposed to natural radiation for billions of years. The stone has a clear and attractive undertone alongside a strong ‘Inner-Grade’ with very little colorless patches.

Total quality score: 11

To review the GIA Report Click here  (5172080253)

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Lot #1747

1.53 carat fancy vivid green oval shape, VS2

High catalog estimation: $1,249,020 per carat

A rare vivid green with exceptional visual characteristics. Strong ‘Inner-Grade’ and almost no colorless patches around the face-up view of the stone. The undertone is clear and not furnished with a brown or yellow undertone.

Total quality score: 12

To review the GIA Report Click here  (6167654693)

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Lot #1716

1.62 carat fancy purple-pink cushion modified brilliant-cut, VS2

High catalog estimation: $196,605 per carat

According to the GIA the stone has a significant amount of purple in the color mix, while pink is the body color of the diamond, the presence of purple is cooling the warmth of the pink and creates a favorable “sweet” appearance. The ‘Inner Grade’ is above average as well as the color dispersion.

Total quality score: 12

To review the GIA Report Click here  (5181867196)

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Lot #1715

3.35 carat fancy vivid orangy yellow pear shape, VVS2

High catalog estimation: $106,484 per carat

A highly saturated Pear shape diamond with no traces of brown or green undertone in the hue. The stone has low depth percentages which creates some colorless areas in the table area when tilting the stone.

Total quality score: 11

To review the GIA Report Click here  (2171115974)

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Lot #1695

4.08 carat fancy vivid yellow step cut, VS1

High catalog estimation: $68,696 per carat

Color dispersion in Emerald cuts in comparison to fancy shapes are usually measured by less stringent parameters, having said that, in sharp contrast to the catalog image, this stone exhibits poor color dispersion with a large colorless area in the center of the table.

Total quality score: 8

To review the GIA Report Click here  (2195197447)

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Lot #1694

5.58 carat fancy vivid yellow step cut, IF

5.55 carat fancy vivid yellow step cut, IF

High catalog estimation: $125,912 per carat

A pair of vivid yellow Emerald cut diamonds with relatively low visual compatibility and low color dispersion on both diamonds. The facet alignment on the two stones is quite different as well as their table size.

Total quality score: 8

To review the GIA Report Click here  (1102852493)

To review the GIA Report Click here  (2135155758)

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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, the color dispersion is not a gemological quality and has only to do with cutter proficiency.