Pre-Auction Analysis: Christie’s Hong Kong, October 29 th, 2024

Our Christie’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 1825

Description: 3.13 ct, Fancy Yellow, Cushion, VS1
High Auction Estimation: $4,937 pc
Price Realized: $6,734 pc
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 3.30 Carat which is ~5.7% Larger than the average

Analysis: A 3.13-carat Fancy Yellow cushion-cut diamond with a solid Inner-Grade and an insignificant Undertone in the hue. The diamond’s face-up appearance is slightly larger relative to its weight, with colorless patches visible on the crown.

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Lot 1826

Description: 2.06 ct, Fancy Intense Yellow, Round, VS2
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 2.49 Carat which is ~20.9% Larger than the average

High Auction Estimation: $38,629 total
Price Realized: $89,172 total
Analysis: A unique, matching pair of Fancy Intense Yellow Round Brilliant-Cut diamonds with exceptional compatibility. Beyond sharing identical visual assets and proportions, they both exhibit  yellow fluorescence—a feature that enhances the hue of any yellow diamond. It is likely they were cut and polished from the same rough, as yellow fluorescence is rare in yellow diamonds. Although the GIA reports are dated August 2020, the combination of table size (62/64%), depth (56/57%), and open culet suggests these diamonds were probably crafted in the final decade of the 20th century.

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Lot 1827

Description: 14.17 ct, Fancy Yellow, Pear, VS1
High Auction Estimation: $7,270 pc
Price Realized: $11,442 pc
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 15.85 Carat which is ~11.9% Larger than the average

Analysis: A large Fancy Yellow Pear-Shape diamond cut and polished in a traditional colorless diamond style, resulting in very low Color Dispersion, with much of the diamond’s face-up appearing colorless. It also exhibits a noticeable warm Undertone reinforcing its Inner-Grade and strong blue fluorescence. The attached Diamond Diary Report reveals that the diamond’s face-up appearance is close to that of a 16-carat, a positive feature that may help offset some of its visual flaws.   

Quality Remark: Low Dispersion and Undertone – Strong Blue

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Lot 1828

Description: 20.02 ct, Fancy Intense Yellow, Oval, VS2
High Auction Estimation: $22,512 pc
Price Realized: $19,437 pc
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 20.08 Carat which is ~0.3% Larger than the average

Analysis: A large Fancy Intense Yellow Oval-Cut diamond with a soft Inner-Grade and very good Color Dispersion, leaving only minor colorless areas in the crown. The strong blue fluorescence has minimal impact on the diamond’s overall color.

Quality Remark: Strong Blue fluorescence 

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Lot 1830

Description: 1.03 ct, Fancy Intense Purplish Pink, Pear, VS1
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 1.19 Carat which is ~15.7% Larger than the average

Description: 1.03 ct, Fancy Intense Purplish Pink, Pear, VS1
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 1.29 Carat which is ~26.0% Larger than the average

High Auction Estimation :$37,504 pc
Price Realized: $236,152 pc
Analysis: Two Fancy Intense Purplish Pink Pear-Shape diamonds with a low Inner-Grade and Color Dispersion, resulting in prominent colorless areas under the table. The purple Undertone seen in the images is less appealing in person. 

Quality Remark: Low Inner-Grade and Dispersion 

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Lot 1833

Description: 4.39 ct, Fancy Vivid Blue, Marquise, SI2
High Auction Estimation: $1,026,586 pc
Price Realized: $684,847 pc
GIA 

Analysis: A 4.39-carat Vivid Blue Marquise-Shape diamond with SI2 clarity. The diamond has been polished with minor modifications to enhance color retention, resulting in a prominent colorless bowtie at the center. An insignificant amount of gray Undertone is present in the hue.

Quality Remark: SI2 Clarity and low Dispersion

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Lot 1896

Description: 21.35 ct, Fancy Vivid Yellow, Radiant, VS2
High Auction Estimation: $53,074 pc
Price Realized: $53,168 pc
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 Fancy Vivid Yellow Radiant-Cut diamond with a soft Inner-Grade, featuring step-cut facets on the crown and a star-burst pattern on the pavilion. The narrow colorless crown around the table limits the overall color impact in the face-up view.

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Lot 1923

Description: 5.02 ct, Fancy Deep Blue, Marquise, IF
High Auction Estimation: $2,052,002 pc
Withdrawn from auction
GIA

Analysis: An important Deep Blue Marquise-Shape diamond with traditional facet alignment, creating a colorless area at the center of the shape suggesting an earlier manufacturing period, despite the GIA report being dated 2018. A strong Inner-Grade is evident in the “Deep” saturation. No gray Undertone visible in the hue.

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Lot 1924

Description: 12.2 ct, Fancy Vivid Orange-Yellow, Oval, VVS2
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 14.33 Carat which is ~17.5% Larger than the average 

Description: 11.96 ct, Fancy Vivid Orange-Yellow, Oval, VS1
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 14.33 Carat which is ~19.8% Larger than the average

High Auction Estimation: $426,368 pc
Price Realized: $330,397 pc
Analysis: Following their successful sale at Christie’s Geneva in May 2016 for $480,000 per carat, these two Vivid Orange-Yellow Oval-Cut diamonds return to the stage for an encore, now mounted in a new pair of earrings with updated reports dated 2023. The Inner-Grade is exceptionally high, with no green or brown Undertone in the hue, though parts of the crown remain colorless. Despite minor contour misalignment, this vibrant pair of ovals represents an exceptional item rarely seen on the market.

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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.