This Sotheby’s and Christie’s Geneva pre-auction analysis has a relatively large amount of blue fancy color diamonds and will focus on visual elements and other general observations that are not expressed on the GIA report, nor on the catalogue, such as, Undertone, Color Dispersion, and Inner-Grade (UDI). We use grades 1, 2, 3, and 4 to describe these features. The grade 4+ is used only in special cases to describe extraordinary visual characteristics. Stones with a total quality score that range from 8 to 12 are considered to be top gems and are suitable for high jewelry, collectables, and so on.

 

It is often difficult to identify these characteristics when viewing fancy color diamonds only in an auction catalogue, especially when the images are heavily processed. All images in this review were taken with an iPhone 7.

 

Important note: We strongly recommend downloading the beta version of the new FCRF app and using the auction calculator. This app lets you calculate your bidding price (per carat), including the house commission, as you follow the lot.

 

Sotheby’s May 16th

Lot No’ 377

14.54 carat fancy vivid blue pear shape diamond, IF

High catalog estimation: US$3.7 million per carat

Price Realized Per Carat- US$ 2.8 million

General

From the classic cutting style of this rare diamond, it is quite clear that the stone was manufactured toward the end of the last millennium. At the time, modified cuts were not very common. Although some people look at any brilliant cut (in a fancy shape) as a virtue, it is in fact a cut that reduces the color dispersion and creates colorless patches. In this case, the colorless “bowtie” in the center and a colorless facet on the point are quite visible, but the overall dispersion is solid. Color Dispersion grade: 3.

Visual Elements

The inner-grade refers to how strong the color is within each intensity grade. In this case, the vivid blue is above average and most likely will meet the expectations of any buyer who is looking to buy a vivid blue. Inner-Grade: 4. 

The undertone in a blue fancy color diamond is measured by the quantity of the gray influence in the chroma of the diamond. The less gray, the higher the undertone grade will be. This 14-carat blue diamond has very little amount of gray influence and exhibits a very high-quality blue. Undertone grade: 4.

Total quality score: 11

FCRF Rarity grade: Iconic (10th out 10 levels)

According to the FCRF rarity calculator, a stone with similar characteristics enters the market once every 25 years and receives the highest rarity grade possible.

 

 

Lot No’ 378

16.00 carat fancy intense pink pear shape diamond, VVS2

High catalog estimation: US$1,125,000 per carat.

Price Realized Per Carat- US$ 958,640

General 

Whether it is done maliciously or in good faith (but out of ignorance), in an attempt to romanticize a lot, auction houses occasionally overload a stone’s description with unnecessary information. The fact an auction house emphasizes that a pink stone has a Type IIa report is what we refer to in this case.

As we published in an article about pink Type IIa, generally speaking, Type IIa pink fancy color diamonds actually suffer from a warm chroma that leans towards an unfavorable orange undertone and also include a visible internal graining that reduces translucency and sparkle. The GIA remark “IN,” regards to the internal graining, supports our case.

Although people might associate these stones with the Golconda allure of colorless diamonds, there is no real reason to mention a Type report with pink diamonds. This stone corresponds to both classic Type IIa characteristics mentioned here: haziness and a warm orange undertone, quite far from the image in the catalogue. 

Visual elements 

The undertone of this 16.00ct intense pink receives a grade 2.

Color dispersion is good, and covers large areas of the face up, and receives a grade 3. 

The inner-grade is 2.

Total quality score: 7

FCRF Rarity grade: One of a kind (9th out of 10 levels)

According to the FCRF data, only 1 out of 194,000,000 polished diamonds will have similar gemological characteristics.

 

 

Lot No’ 371

7.04 carat fancy intense purplish pink cushion cut diamond, VS1

High catalog estimation: US$1.7 million per carat

Price Realized Per Carat- US$ 1.8 million

General

The fact the GIA report calls this old mine cushion–looking diamond a rectangular modified brilliant doesn’t fit the actual look of the stone and might give a certain sense of discomfort to potential buyers. The stone has a very low depth percentage, a fact that makes it look much bigger than it really is.

Evidently, the stone went through minor polishing procedure at a later stage. The facets on the side of the stones are evidence to that.

Visual elements

 Although low color dispersion comes with the territory in the look-alike stones of old mine cushions, the color dispersion in this case is above average and receives a grade 3.

The pink undertone is the first characteristic most professionals look at when evaluating a pink fancy color diamond. The stone has a proper amount of purple and receives a high grade of 4.

The inner-grade is very high and receives a grade of 4 as well.

Total quality score: 11

FCRF Rarity grade: Very Rare (7th out of 10 levels)

Two to four new stones with similar gemological characteristics appear every year in the 5–10ct category.

Lot No’ 363A

3.32 carat fancy vivid blue emerald cut diamond, IF

High catalog estimation: US$2.4million per carat

Price Realized Per Carat- US$ 2.1 million

 General

A fancy vivid blue emerald cut with a very low depth percentage that makes the stone look as large as a 4-carat. The light path is relatively short in all shallow stones; and light path rate in emerald cut diamonds is poor to begin with. These two factors will automatically refrains from any fancy color diamond to hold its color.

Visual elements

In a sharp contrast to the catalog image, the color dispersion of this 3.32-carat diamond is low, especially in the culet, and receives the grade 2.

The inner-grade is very high and receives the grade 4.

The undertone is very close to a dark primary blue with no influences of gray and receives the grade of 4.

Total quality score: 10

FCRF Rarity grade: One of a kind (9th out of 10 levels)

 Lot No’ 364

21.11 fancy pink oval cut diamond, VVS2

High catalogue estimation: US$236,000 per carat

 

General

The stone has a significant amount of internal graining. The trained eye of a professional can detect a certain amount of haziness.

Visual elements

Color dispersion is quite good and receives the grade 3.

Inner-grade is low for a fancy and receives the grade 2.

Undertone is warmer than it looks in the catalogue and receives the grade 3.

Total quality score: 8

FCRF rarity grade: Exceptionally rare (8th out of 10 levels)

 

Christie’s May 17th

Lot No’ 221

4.05 carat fancy deep blue mixed cut diamond, VS1

High catalog estimation: US$1.25million per carat

Price Realized Per Carat- US$ 1.1 million

General

 

A rare blue diamond with an odd modern cut, trying to imitate an old-cut style diamond.

 

Visual elements

This blue diamond has an above-average color dispersion with a colorless culet and receives a grade 3.

The blue undertone is influenced by a significant amount of gray tint and receives a low grade of 2.

Typically, a fancy color diamond with a deep color grade receives a strong inner-grade. In this case, the saturation is not very dark for a deep and the inner-grade is graded 2.

Total quality score: 7

FCRF Rarity grade: Exceptionally rare. (8th out of 10 levels)

Only one out of 72 million polished diamonds above one carat will have similar characteristics.

 

 Lot No’ 204

7.97 carat fancy intense blue cushion cut diamond, VS1

High catalog estimation: US$370,000 per carat

 

General

As seen in our picture, it is quite obvious the catalog image was heavily processed to make it look much better than it really is.

 

The fact that this blue diamond has an “uneven” grade on the GIA report should not disturb buyers who are looking to own a cushion cut diamond with an old look. Many cushions with these characteristics will receive an uneven grade.

Visual elements

Dispersion grade is 2.

The inner-grade on this fancy intense blue diamond is 3.

The undertone is a true primary blue and receives the grade 4.

Total quality score: 9

FCRF Rarity grade: Exceptionally rare (8th out of 10 levels)

Out of all polished diamonds, only 1 in 54,000,000 will have similar characteristics.