Pre-Auction Analysis: Sotheby’s Geneva, May 14th, 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 14 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: 519

Description: 21.35 ct, Fancy Vivid Yellow, Radiant, VS2
High Auction Estimation: $66,592 pc
Price Realized: Didn’t reach the minimum.
Reports: GIA, Rarity, Diary
True Face-Up: Equivalent to that of a 21.88 carat which is ~2.5% larger than the average

Analysis: A large Vivid Yellow radiant cut diamond that features a thin colorless frame around the table. Beneath the table, a well-placed mosaic of color is present. The Inner Grade is weak, and no significant green or brown Undertone is present in the hue.

Visual Assets:
Inner Grade..……………….2
Color Dispersion.………3
Undertone..…………………3
Total Visual Score….8 out of 12

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Lot: 571

Description: Two Fancy Intense Yellow emerald cut diamonds weighing 9.85 and 9.70 ct
High Auction Estimation: $656,188 total
Price Realized:$630,474 Total
Reports: GIA, Rarity, Diary ; GIA, Rarity, Diary
True Face-Up: Equivalent to that of a 15.24 carat which is ~55.0% larger than the average

Analysis: Two large Fancy Intense Yellow emerald cut diamonds, with no modifications in their cut to increase color visibility, indicate they were likely cut before the 1990s. Although both are mounted in a yellow gold cup, the Inner Grade remains low, as does the Dispersion. Traders who decide to recut the diamonds will have room for improvement in overall appearance and clarity. It’s important to note that the face-up appearance is significantly larger in relation to their carat weight, a critical factor that could impact their pricing.

Visual Assets (9.85 ct):
Inner Grade..……………….1
Color Dispersion.………1
Undertone..…………………3
Total Visual Score….5 out of 12

Visual Assets (9.7 ct):
Inner Grade..……………….1
Color Dispersion.………1
Undertone..……….……….3
Total Visual Score….5 out of 12

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Lot: 582

Description: 3.74 ct, Fancy Light Pink, Pear, VS1
High Auction Estimation: $64,332 pc
Price Realized: $61,764 pc
Reports: GIA, Rarity, Diary
True Face-Up: The Diamond’s face-up view appears true to its carat weight.

Analysis: A 3.74 Fancy Light Pink pear shape with high visual properties. The strong blue fluorescence appears to have very little effect on the overall appearance of the diamond.

Visual Assets:
Inner Grade..……………….4
Color Dispersion.………4
Undertone..…………………3
Total Visual Score….11 out of 12
Quality Remark: Strong blue

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Lot: 601

Description: 2.47 ct, Fancy Intense Yellowish Green, Old Mine, SI2
High Auction Estimation: $283,374 pc
Price Realized: $300,555 pc
Reports: GIA, Rarity, Diary
True Face-Up: Equivalent to that of a 3.38 carat which is ~36.8% larger than the average

Analysis: An Old Mine Intense Yellowish-Green cushion cut diamond, mounted in a ring by JAR, reveals under a 45-degree angle view beneath the pavilion that the diamond’s color hasn’t reached its full potential. No gray Undertone is visible, and the amount of yellow modifier is mild, giving a solid Green color sensation.

Visual Assets:
Inner Grade..……………….3
Color Dispersion.….……1
Undertone..…………………4
Total Visual Score….8 out of 12
Quality Remark: SI2, Fair Symmetry

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Lot: 608

Description: 3.03 ct, Fancy Intense Blue, Pear, I1
High Auction Estimation: $397,033 pc
Price Realized: $300,539 pc
Reports: GIA, Rarity, Diary
True Face-Up: The Diamond’s face-up view appears true to its carat weight.

Analysis:  A fancy Intense Blue pear-shaped diamond that features a visible gray undertone and a large feather on the table (image 2). The colorless areas on the crown enhance the optical illusion of even a longer pear shape.

Visual Assets:
Inner Grade..……………….3
Color Dispersion.………3
Undertone..…………………2
Total Visual Score….8 out of 12
Quality Remark: Visible I1 clarity

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Lot: 609

Description: 3.06 ct, Fancy Pink-Purple, Pear, VS2
High Auction Estimation: $196,570 pc
Price Realized: $160,242 pc
Reports: GIA, Rarity, Diary
True Face-Up: Equivalent to that of a 3.26 carat which is ~6.7% larger than the average

Analysis:  A 3.06 Fancy Pink-Purple pear shape with low Color Dispersion and Inner-Grade. Although the report indicates it is a brilliant cut pear shape, it is clear it underwent a modification not noted on the report. Four new small facets were added around the culet in an attempt to fill the colorless area in the centre of the shape, however, it appears as if this was an unsuccessful attempt.

Visual Assets:
Inner Grade..……………….2
Color Dispersion.………2
Undertone..…………………3
Total Visual Score….7 out of 12

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Lot: 610

Description: 101.29 ct, Fancy Vivid Yellow, Old-Mine cushion, VS2
High Auction Estimation: $70,182 pc
This lot has been withdrawn from the auction.
Reports: Gia, Diary
True face-up: as old mine diamonds tend to appear smaller, this feature is of less relevance.

Analysis: This iconic cartier piece from the beginning of the century needs no special introduction, as it is among the most iconic fancy color diamonds in the world. The diamond was cut in a different century, yet it has a modified cut, which leads us to believe it was recut along the way to achieve the vivid grade and better color dispersion.

Visual assets:
Inner grade..……………….3
Color dispersion.………3
Undertone..…………………3
Total visual score….9 Out of 12

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Lot: 614

Description: 1.01 ct, fancy intense blue, marquise, vs1
High auction estimation: $292,361 pc
Price realized: $346,769 pc

Analysis: A fancy intense blue marquise cut diamond that features an insignificant amount of gray undertone in the hue. the facet alignment appears to be unsymmetrical, creating a colorless area on one side of the shape (at the 6 o’clock mark).

Visual assets:
Inner grade..……………….3
Color dispersion.………2
Undertone..…………………3
Total visual score….8 Out of 12
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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, providing insights into the color’s intensity and richness. From grade 1, indicating the faintest saturation, to grade 4+, reserved for the most vivid saturation levels, this grading reveals the depth of a diamond’s color.

Color dispersion Examines how evenly the color is distributed across the diamond’s face-up view. This aspect ranges from grade 1, showing noticeable colorless areas, to grade 4+, indicating a flawless color spread.

Undertone Evaluates the subtle hue influences within the diamond’s color. The undertone grade reflects the diamond’s color fidelity and its alignment with the desirable aesthetic standards.

From grade 1, indicating a significant presence of altering hues that might dilute the primary color’s intensity. To grade 4+, reserved for diamonds where the undertone enhances the primary color, making it exceptionally desirable.

Our innovative true face-up calibration grade also offers invaluable insights into how a diamond’s carat weight is presented visually, adding another dimension to our comprehensive analysis.

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.