Pre-Auction Analysis: December 10th 2019, Sotheby’s New-York, Magnificent Jewels

Our Sotheby’s, New-York Pre-Auction Analysis focuses on elements that are hidden from the unprofessional eye. We will describe the important visual elements for those who cannot attend the preview and discuss characteristics such as: Undertone, Color Dispersion, and Inner-Grade (UDI; a detailed explanation appears at the bottom of this article). When we analyze and grade any Fancy Color Diamond it is always done in relation to its GIA grade.

We use grades 1, 2, 3, and 4, 1 being the lowest grade. Grade + 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 red remark, are considered to be “Gems” and are generally sought after by high-end jewelry brands, 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 11pro, no filters were applied.
• All auction valuations are per carat and in US Dollars.

Lot # 423

7.00 carat Fancy Blue, Pear, VS2. High catalog estimation: $400,000‬ per carat

Market Prevalence: A similar diamond enters the market once every 3 – 5 years

Result: Didn’t reach the minimum

A relatively large, fancy blue, pear shape diamond. The color dispersion is poor, mainly visible at the tip and at the rounded base of the shape. The gray undertone is not very noticable and the inner-grade is low. 

Total Visual Score: 7 out of 12

To review the GIA Report Click here -> 10733869

Lot # 500

7.55 carat Fancy Deep Grayish Blue, Cushion, SI2. ‘THE INDIAN BLUE’. High catalog estimation: $1,059,602 per carat

Price realized: $ 879,788 pc

An impressive, old mine-cut, blue diamond, with a gray modifier. The stone’s color is situated on the axis between black and “Ink-blue”. In fact, it is extremely dark and could have been easily graded as “Dark” instead of “Deep”. The “Fair” symmetry is common in antique diamonds, as well as the open culet. Due to the thick color and low transparency, the SI2 clarity is not visible to the naked eye.

Our three parameters are not applicable in stones with a gray modifier which are graded as “Deep”.    

Total Visual Score: –  out of – 

To review the GIA Report Click here -> 6173309927

Lot # 497

14.37 carat Fancy Vivid Yellow, old mine cushion, SI1. High catalog estimation: $167,014 per carat 

Market Prevalence: Not applicable for old mine cut

Price realized: $ 143,354 pc

A large, vivid yellow, old-mine cut diamond, with exceptional and rarely seen visual characteristics. The inner-grade is at its highest possible grade while the color covers all possible areas on the face up view. The yellow hue is absolute, with no green or brown undertone. The white crystal under the table is slightly visible to the naked eye and the table is not centered. 

Total Visual Score: 12++ out of 12 

To review the GIA Report Click here -> 5201658548

Lot # 415

5.06 carat Fancy Pink-Purple, Radiant, VVS2. High catalog estimation: $197,628 per carat

Price Realized: $ 169,960 pc

This 5.06 radiant has a noticeable purple body color and a pink modifier. This combination of color often creates an anemic “steely” undertone, moreover when the girdle is ringed with white gold. The inner-Grade is week and there are numerous colorless patches in the crown area.   

Total Visual Score: 7 out of 12

To review the GIA Report Click here -> 2205522518

Lot # 477

2.07 carat Fancy Pink, Radiant, IF. High catalog estimation: $169,082 per carat

Market Prevalence: 1 to 2 similar diamonds enter the market yearly

Price realized: $ 169,082 pc

A fancy pink diamond, with a strong inner-grade bordering the “Intense” saturation. The 59% depth makes the stone look much larger in relation to its weight, and the color is dispersed all over the face-up view of the stone. A soft purple undertone generates here a pleasant cold pink hue,

Total Visual Score: 11 out of 12

To review the GIA Report Click here -> 1142227968

Lot # 445

0.70 carat Fancy Vivid Green-Blue, Oval, I1. ‘THE ABACO BLUE’ by WILLIAM GOLDBERG. High catalog estimation: $285,714 per carat

Price realized: $ 107,142 pc

A rare color combination, especially in the “vivid” grade. The undertone is well aligned with the GIA color description. There are some colorless patches in the crown area and the Vivid inner-grade is average. We can assume that the need to keep it above the 0.70 carat overcame the need to polish the stone within market standards, as such, it was left with a “fair” symmetry.

Total Visual Score: 9 out of 9 

To review the GIA Report Click here -> 2155291378

Lot # 485

2.58 carat Fancy Grayish Blue, Marquise, VS2. High catalog estimation: $77,519 per carat 

Price realized: $ 333,333 pc

A Blue marquise with 15-20% gray in the color composition and 70% depth. The undertone is aligned with the GIA color description. The color dispersion is low due to the fact that the stone is cut as a colorless diamond.  

Total Visual Score: 8 out of 12 

To review the GIA Report Click here -> 1186961476

Lot # 517

13.97 carat Fancy Intense Yellow, Radiant, SI2. High catalog estimation: $12,526 per carat

Market Prevalence: 1 to 2 similar diamonds enter the market yearly

Price realized: $ 11,632 pc

A radiant cut diamond with rounded corners, with 62% depth. The stone attains average visual characteristics. The SI2 clarity stems from several white feathers scattered on the pavilion and the crown which are not visible to the naked eye.

Total Visual Score: 9 out of 12

To review the GIA Report Click here -> 2201570573

Lot # 567

15.00 carat Fancy Yellow, Radiant, VVS. High catalog estimation: $11,666 per carat

Market Prevalence: 1 to 2 similar diamonds enter the market yearly

Price realized: $ 12,500 pc

A fancy yellow, radiant cut diamond, with a large table (72%). The crown is mostly colorless as well as some other parts under the table. The inner-grade is solid and the undertone is average

Total Visual Score: 9 out of 12 

To review the GIA Report Click here -> 6204442195

Lot # 479

0.76 carat Fancy Intense Bluish Green, Cushion, VS2. High catalog estimation: $197,368 per carat

Price realized: $ 164,473 pc

A fancy intense green diamond with 15-20% blue in the color composition. 

The table is extremely large (78%) and the depth percentage is quite low (58%), a feature that makes the stone look larger in relation to its carat weight. The intense inner-grade is strong, bordering to a vivid. The GIA is dated 2012. 

 Total Visual Score: 10 out of 12

To review the GIA Report Click here -> 2145982284

General

We use 1, 2, 3, 4, and 4+ to grade the three visual elements that GIA is silent about, however they 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 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 to 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.