Pre-Auction Analysis: Sotheby’s New York, June 7th, 2024

Pre-Auction Analysis: Sotheby’s New York, June 7th, 2024, 

Our Sotheby’s Magnificent Jewels Pre-Auction Analysis focuses on elements that are not always visible to the untrained eye. We discuss characteristics such as Inner-Grade, Color Dispersion, and Undertone – collectively termed IDU. Professionals use the IDU method intuitively when analyzing a Fancy Color Diamond. The acronym we use makes these elements easier to remember. 

Members who read this analysis should see it as a valuable supplement to the GIA report. A detailed explanation of the FCRF’s grading methodology can be found at the end of this article. We recommend reviewing it closely to broaden one’s professional vocabulary for describing fancy color diamonds to clients.  

Please note that we analyze and grade diamonds under LED lights and relative to their grade on the GIA report.

The Grades

We use grades 1, 2, 3, and 4, with 1 being the lowest grade. Grade “4+” is granted in rare cases and denotes diamonds with exceptional characteristics. diamonds that receive a minimum total IDU score of 9 without a red remark pass the industry premium threshold and can be traded easily. Fancy Color Diamonds that are graded 10 or above (without a quality remark) are usually sought after by high-end jewelers and collectors.

For your convenience, we have added direct links to diamonds’ GIA reports and FCRF rarity stats.

• All images in this analysis were taken with an iPhone 13 Pro; no filters were applied.
• All auction valuations are per-carat and listed in US Dollars.
• The FCRF evaluates chosen diamonds during each auction based on expert judgments.

Disclaimer

This analysis reflects the opinions of the FCRF professional team. It does not constitute a recommendation to buy or not buy a particular diamond. Buyers assume the responsibility of verifying any information with the auction house. At times, mistakes can happen in the visual analysis and report placement. Therefore, one should not rely solely on this analysis for buying purposes.

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Lot 19

Description: Two Fancy Yellow, Oval cut diamonds, IF weighing 6.01 ct, and 5.5 ct
High Lot Estimation: $350,000 total
Price Realised: $288,000 total
GIA Rarity Diary ; GIA Rarity Diary
True Face-Up: On average, both face ups appear equivalent to a 7.38 ct

Analysis: Two Fancy Intense Yellow oval cut diamonds that exhibit different outlines, preventing them from appearing as a matching pair. Based on their classic facet alignment, it is evident they were manufactured before the 1990s. The polishing style does not consider Color Dispersion, resulting in the yellow color being concentrated at the edges, leaving the center of the diamonds mostly colorless. The Inner-Grade is solid, with no significant green or brown Undertones in the hue. A notable benefit of this older cutting style is that the weight of the stones translates to a very large appearance, 28% on average according to the true face-up tool.

Quality Remark: Low dispersion

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Lot 50

Description: 20.02 ct, Fancy Intense Yellow, Radiant, VVS2
High Lot Estimation: $24,976 pc
Price Realised: $19,181 pc
GIA Rarity Diary
True Face-Up: Appears true to its carat weight

Analysis: A large Fancy Intense Yellow radiant diamond with a step cut crown and a starburst facet on the pavilion, resulting in a mixed cut definition on the report. The steep crown angle creates large dark, colorless patches around the table. These dark, colorless patches detract from the diamond’s aesthetic integrity as they affect the outline of the shape and disrupt the color consistency on the face-up view. The Inner-Grade is at its highest grade, bordering on the Vivid grade and no green or brown Undertone is visible in the hue.

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Lot 52

Description: 2.82 ct, Fancy Intense Blue-Green, Radiant, SI1
High Lot Estimation: $248,227 pc
Price Realised: Didn’t reach the minimum
GIA Rarity Diary
True Face-Up: Equivalent to that of a 0.32 carat which is ~18.6% larger than the average

Analysis: A Fancy Intense Blue-Green radiant cut with a low Inner-Grade and a very pleasant Undertone, meeting our expectations from the color description on the report. The colorless patches on the crown give the diamond a grade of 3. 

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Lot 57

Description: Two Fancy Yellow, Radiant cut diamonds, VVS2 weighing 16.77 ct and 16.37 ct
High Lot Estimation: $400,000 total
Price Realised: $420,000 total
GIA Rarity Diary ; GIA Rarity Diary
True Face-Up: Appears true to its carat weight

Analysis: A large matching pair of elongated Fancy Yellow radiant cut diamonds with a solid Inner-Grade. Their face-up appearance is true to their carat weight.

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Lot 85

Description: 3.36 ct, Fancy Intense Pinkish Purple, Oval, SI2
High Lot Estimation: $446,429 pc
Price Realised: Didn’t reach the minimum
GIA Rarity Diary
True Face-Up: Equivalent to that of a 4.27 carat which is ~26.9% larger than the average

Analysis: An Intense Purple oval cut diamond with a pink modifier. The SI2 clarity results from a group of inclusions commonly referred to in industry jargon as “bubbles” due to their round and transparent nature. Other than a large dark colorless area in the center of the crown, the color is well dispersed across the face-up view, and the Undertone meets our expectations from the GIA description. This oval’s True Face-Up correlates to a diamond that appears 30% larger.

Quality Remark: SI2

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Lot 86

Description: 1.41 ct, Fancy Vivid Green-Blue, Radiant, I2
High Lot Estimation: $390,071 pc
Price Realised: Didn’t reach the minimum
GIA Rarity Diary
True Face-Up: Subtly Smaller than Standard

Analysis:  A fancy color diamond with an exceptional combination of color and saturation. According to the Rarity Report, a diamond with these characteristics comes into the market once every 8 to 12 years. The combination of green and blue in the Vivid grade inherently presents a high Undertone grade. Although significant colorless patches surround the crown, the I2 clarity is mostly disguised by the strong saturation of the stone. 

Quality Remark: I2, face up appears small

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Lot 87

Description: 0.73 ct, Fancy Purplish Red, Pear, SI2
High Lot Estimation: $821,918 pc
Price Realised: $493,151 pc
GIA Rarity Diary
True Face-Up: Equivalent to that of a 0.75 carat which is ~2.7% larger than the average

Analysis: Diamonds with a red body color are among the rarest and most coveted in the fancy color market. Those with a purple modifier, like this one, generally have a brighter and more pleasant appearance than straight red diamonds, which may appear dark or exhibit a warm color sensation.

Due to the high demand for diamonds with a red body color, manufacturers often modify deep or vivid pink diamonds into a certain facet alignment to reflect the precise amount of light within the diamond. This process can compromise the shape, ratio, and color dispersion, as seen in this case, to receive the Red color grade from the GIA.

Quality Remark: Low dispersion, odd ratio

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Discover the IDU Grading Standard

Our pre-auction analysis leverages the IDU Grading Standard to evaluate fancy color diamonds, focusing on three key visual attributes not covered by GIA: Inner-Grade, Undertone, and Color Dispersion. These elements provide deeper insights into a diamond’s color intensity, hue influences, and color evenness—factors critical to its beauty and value. Additionally, our True Face-Up calibration reveals how a diamond’s carat weight translates to its visual presence.

Inner-Grade measures the saturation strength within the GIA-defined categories, determining the level of saturation. 

Grade 1 places the saturation in doubt, indicating it borders on the saturation below. 

Grade 2 is a weak saturation, 

Grade 3 refers to a solid saturation, 

Grade 4 borders on one saturation above. In the vivid category, 

Grade 4+ is reserved for exceptional saturation.

Color Dispersion examines literally how well the color mosaic is dispersed across the diamond’s face-up view. 

This aspect ranges from Grade 1, showing noticeable colorless areas, to Grade 4+, indicating perfect dispersion.

Undertone evaluates the subtle color influences within the diamond’s color, such as brightness or muted tones. 

The undertone grade reflects the diamond’s color sensation and how well it meets our expectations of the color. 

Grade 1 indicates a significant presence of another color. 

Grade 2 indicates a mild foreign sensation. 

Grade 3 indicates an insignificant undertone (most abundant). 

Grade 4 is the pure form of the color.

Grade 4+ is reserved for pink diamonds where the undertone enhances the primary color, making it exceptionally desirable.

For an in-depth exploration of our grading methodology and how it enhances the valuation of fancy color diamonds, we invite you to read the full article.