Our Pre-Auction analysis focuses on some unusual 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 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 most suitable for high-end jewelry, collectors, and the investment community. A detailed explanation of our grading system is at the bottom of this article.

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.

Christie’s Hong Kong Magnificent Jewels, May 29th, 2018


Lot #2093

8.01 carat fancy vivid blue pear shape, IF

High catalog estimation: $3,084,628 per carat

An elongated vivid blue pear shape with no gray undertone and a below average inner-grade in its category. Diamonds with low depth percentage usually achieve a premium for their relatively large look. However, in fancy color diamonds, low depth percentage might jeopardize the color dispersion, as we see in this stone. Tilting the stone gently reveals interchanging “see-through”  areas on the rounded side. The round brilliant diamond on the top has a very strong inner-grade, good color dispersion, and undertone. It is a modified round brilliant with a large visible feather on the table. 

Vivid blue pear shape

Inner-Grade Color Dispersion Undertone
2 3 4

Total quality score: 9

Lot #2093

To review the GIA Report Click here 


Lot #1904

10.04 carat fancy vivid yellow cushion-shaped, VS2

High catalog estimation: $101,972 per carat

A vivid yellow cushion cut diamond with a very good color dispersion and a clear yellow undertone. The cushion has a very high depth percentage (76.6%), which creates a small face-up appearance in relation to its weight.

When looking at the comments on the GIA report, you will see an indication of a laser inscription of the word ‘Zimi’ (should be spelled ‘Zimmi’), apparently to give the illusion that the stone was unearthed in Sierra Leone in order to grant the stone the ‘allure’ of an exceptional vivid yellow unearthed next to the Zimmi village. Unfortunately, this stone  has a medium blue fluorescence, a characteristic that does not correspond with yellow fancy color diamonds from this area.    

Inner-Grade Color Dispersion Undertone
4 4 3

Total quality score: 11

Additional Grading Information

 

Lot #1904

To review the GIA Report Click here 


Lot #2091

8.09 carat fancy vivid yellow oval brilliant shape, VVS2

High catalog estimation: $189,772 per carat

A large old-mine vivid yellow oval with a very strong inner-grade. The undertone has no brown or green influence in the hue and exhibits an absolute yellow. The color dispersion is quite low, but it corresponds with the periodic style of the cut. Therefore a low color dispersion is inherent and will receive a relative grade to the cutting style. In regards to the GIA report, it’s a shame the plot on the report completely misrepresents the facet alignment of the diamond.      

Inner-Grade Color Dispersion Undertone
4 3 4

Total quality score: 11

Lot #2091

To review the GIA Report Click here 


Lot #2090

12.85 carat fancy intense orangy pink oval shape, VVS1

High catalog estimation: $647,156 per carat

In sharp contrast to the catalog image, the undertone of this orangy pink oval is very warm and leans towards brown. The color dispersion is below average with a colorless frame in the crown area, while the four facets surrounding the culet create a large colorless “see through” area. In order to camouflage this problem, the pink gold construction on the bottom of the ring covers the colorless culet and gives the illusion of a better color dispersion.

Inner-Grade Color Dispersion Undertone
3 2 2

Total quality score: 7

Lot #2090 / 1

Lot #2090 / 2

To review the GIA Report Click here 


Lot #2088

2.24 carat fancy purplish pink heart shape, VS2

1.95 carat fancy blue heart shape

High catalog average estimation: $244,273 per carat

A ‘Toi et Moi’ ring with pink and blue fancy color heart shape diamonds.

The Fancy Blue Heart Shape

The stone has a large indented natural on the right shoulder that would have given the stone a low clarity grade. This is probably the reason the GIA issued the “Color Only” report. Knowing the location of the crack makes it easy to spot with the naked eye.

The undertone has no gray influence and exhibits an absolute blue. The inner-grade is very strong and easily mistaken to be an intense blue. The color dispersion is very high as well.

The Fancy Pink Heart Shape

The stone has a strong inner-grade, a pleasant undertone with almost no orange influence and very few colorless areas.

Pink

Inner-Grade Color Dispersion Undertone
3 3 3

Blue

Inner-Grade Color Dispersion Undertone
4 4 4

Total quality score: pink 9

Total quality score: blue 12 (color only report)

Lot #2088

To review the GIA Report Click here (Blue)

To review the GIA Report Click here (Pink)


Lot #2085

2.35 carat fancy intense blue pear shape, IF

High catalog estimation: $816,624 per carat

Although smartly mounted in a ring with a pink diamond halo, some of the visual elements remain low. The stone has colorless patches in the crown area and in the center. The inner-grade is above average, but in this case, it’s a result of a strong presence of a gray undertone, creating a darker look.    

Inner-Grade Color Dispersion Undertone
3 2 2

Total quality score: 7

Lot #2085

To review the GIA Report Click here 


Lot #1903

8.02 carat fancy vivid yellow emerald-cut, IF

7.76 carat fancy vivid yellow square shaped, IF

High catalog estimation: $185,262 per carat

High catalog estimation: $191,469 per carat

A matching pair of square Emerald cut diamond earrings with high compatibility in color and in measurements. The color dispersion is average for a fancy color Emerald cut, and so is the undertone. The inner-grade is above the average vivid.

Inner-Grade Color Dispersion Undertone
3 3 3

Total quality score: 9

Lot #1903

To review the GIA Report Click here (Emerald)

To review the GIA Report Click here (Sqaure)


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.