Pre-Auction Analysis: NY Magnificent Jewels, Sotheby’s December 4th, Christie’s December 5th, 2018
Our Pre-Auction Analysis focuses on elements that are hidden from the non-professional eye. 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). Grade 4+ is granted in rare cases and stands for stones with 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 to 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.
Sotheby’s, NY Magnificent Jewels, December 4th 2018
Lot #98
10.62 carat Fancy Vivid Blue Pear shape, VVS1
High catalog estimation: $2,824,859 per carat
A large vivid blue pear shape with very good visual characteristics. Two visible colorless areas are situated on each side of the stone, and no significant gray undertone is present in the hue. The inner-grade is strong and exhibits a stronger saturation than the average vivid blue diamond.
| Inner-Grade | Color Dispersion | Undertone |
| 4 | 3 |
3 |
Total Quality Score: 10
To review the GIA Report Click here (12988260)
Lot #95
2.76 carat Fancy Intense Purple-Pink Pear shape, VVS1
High catalog estimation: $579,710 per carat
According to the GIA color description, this stone has approximately 30–40% “purple” in the color mix, which creates a colder, more desirable pink undertone, in most cases. The inner-grade is quite low and reduces the overall beauty of the stone.
| Inner-Grade | Color Dispersion | Undertone |
|
2 |
3 |
3 |
Total Quality Score: 8
To review the GIA Report Click here (2195146853)
Lot #56
6.46 carat Fancy Orangy Pink cut-cornered rectangular step cut, VVS2
High catalog estimation: $123,839 per carat
In comparison to most “orangy pink” fancy color diamonds, the undertone is quite pleasant and doesn’t come across as being too warm. The color dispersion is low, even in comparison to a step cut, as well as the inner-grade. The large four corners of the shape and the low depth percentage give the diamond a genuine Art Deco look.
|
Inner-Grade |
Color Dispersion | Undertone |
| 2 | 2 |
3 |
Total Quality Score: 7
To review the GIA Report Click here (1186638798)
Christie’s, NY Magnificent Jewels, December 5th 2018
Lot #373
8.08 carat Fancy Vivid Blue Cushion shape, VS2
High catalog estimation: $2,227,723 per carat
Looking at the chips and bruises on the surface of the stone and the facet alignment, it is reasonable to assume the diamond was polished in the 1950s or the 1960s. The inner-grade is strong, with very little gray undertone. Although the stone is cut as an old-mine cushion with low depth percentage, the color is dispersed in a very good manner.
| Inner-Grade | Color Dispersion | Undertone |
|
4 |
4 |
4 |
Total Quality Score: 12
To review the GIA Report Click here (2191711258)
Lot #356
15.56 carat Fancy Intense Pink Heart-modified Brilliant cut, VS1
High catalog estimation: $777,208 per carat
A large, pink, heart shape diamond with average color dispersion and a warm pink undertone.
| Inner-Grade | Color Dispersion | Undertone |
|
3 |
3 |
2 |
Total Quality Score: 8
To review the GIA Report Click here (5161125444)
Lot #242
10.49 carat Fancy Vivid Yellow Rectangular cut, IF
High catalog estimation: $57,197 per carat
Square vivid yellow Emerald cut diamond with average inner-grade and undertone.
From the face up, one can see many colorless areas between the four yellow corners of the bottom pavilion, which grants the stone a low dispersion grade.
| Inner-Grade | Color Dispersion | Undertone |
|
3 |
2 | 3 |
Total Quality Score: 8
To review the GIA Report Click here (5182930943)
Lot #222
3.01 carat Fancy Vivid Green Cushion modified Brilliant cut
High catalog estimation: $166,113 per carat
Vivid green diamonds are very rare in all sizes, especially when they are above 3 carats.
However, rarity is not always enough to make a diamond very valuable. This relatively large vivid green stone has a very low color dispersion and a large black crystal – visible to the naked eye – on the table. The fact the stone has a “Color Only” report probably indicates the clarity was supposed to be I1.
| Inner-Grade | Color Dispersion | Undertone |
|
2 |
1 |
3 |
Total Quality Score: 6
To review the GIA Report Click here (5101267227)
Lot #95
16.23 carat Fancy Intense Yellow cut cornered square step cut, VS1
High catalog estimation: $30,807 per carat
A large, yellow step cut diamond. The inner-grade is solid and above the average vivid saturation. The color dispersion is quite high within the table area, but the crown area is completely colorless and creates a prominent frame.
| Inner-Grade | Color Dispersion | Undertone |
|
3 |
2 |
3 |
Total Quality Score: 8
To review the GIA Report Click here (17465206)
Lot #59
8.09 carat Fancy Vivid Yellow Oval Brilliant cut, VVS2
High catalog estimation: $148,331 per carat
An unusual vivid yellow, old-mine-looking oval. According to Christie’s description, the diamond and ring are from the mid-1920s, which matches the facet alignment and the open culet on the stone. However, the “Very Good” “Polish” and “Symmetry” gives away the fact that the stone went through a thorough polishing procedure.
The inner-grade is outstanding and receives a score of 4+.
| Inner-Grade | Color Dispersion | Undertone |
|
4+ |
3 |
3 |
Total Quality Score: 10+
To review the GIA Report Click here (2171324709)
General
We use 1, 2, 3, 4, and 4+ to grade the three visual elements that GIA is silent about, however, impact the 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 Bue 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.
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