Pre-Auction Analysis: Phillip’s Hong Kong, October 3rd, 2024

Our Phillips The Hong Kong Jewels Auction 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 534

Description: 3.55 ct, Fancy Deep Yellow, Pear, VVS2.
High Auction Estimation: $12,958 pc.
Price Realized: $12,900 pc.
GIARarityDiary
True Face-Up: Equivalent to that of a 4.42 carat which is ~24.6% larger than the average.

Analysis: A 3.55-carat, fancy deep yellow pear-shaped diamond with a 1.4 ratio features traditional facet alignment, resulting in a prominent colorless “bowtie” effect at the center. Strong saturation is inherent in deep yellow diamonds.

Quality Remark: Low dispersion.
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Lot 572

Description: 21.7 ct, Fancy Vivid Yellow, Pear, VS2.
High Auction Estimation: $41,475 pc.
Price Realized: Didn’t reach the minimum.
GIA   Rarity   Diary
True Face-Up: True to its carat weight.

Analysis: A very large, vivid yellow pear-shaped diamond with strong blue fluorescence, resulting in a slightly hazy appearance and a low inner-grade.

Quality Remark:  Strong blue fluorescence.

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Lot 577

Description: 5.03 ct, Fancy Vivid Yellow, Round, VVS1.
High Auction Estimation: $153,082 pc.
Price Realized: Didn’t reach the minimum.
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 5.21 carat which is ~3.6% larger than the average.

Analysis: A relatively large, vivid yellow round brilliant cut diamond with a very strong inner-grade. No green or brown undertones are visible in the color.

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Lot 598

Description: 16.08 ct, Fancy Vivid Yellow, Radiant, VVS1.
High Auction Estimation: $39,801 pc.
Price Realized: $30,503 pc.
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 16.3 carat which is ~1.4% larger than the average.

Analysis: A large, vivid yellow radiant-cut diamond with a low inner-grade, bordering on the “Intense” grade. Prominent colorless patches are visible across the face-up view.

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Lot 599

Description: 3.81 ct, Fancy Grey-Blue, Radiant, VS1.
High Auction Estimation: $262,467 pc.
Withdrawn from auction.
GIA   Rarity   Diary
True Face-Up: Equivalent to that of a 3.87 carat which is ~1.5% larger than the average.

Analysis: A 3.81-carat radiant cut diamond featuring approximately 40% gray and 60% blue in the hue. The gray color contributes to strong saturation. Colorless patches are visible on the crown area. The GIA certification is dated 2011.

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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.