Pre-Auction Analysis: Sotheby’s Hong Kong, April 6th, 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 1633

Description: 12.28 ct, Fancy Yellow, Radiant, VVS1
GIA, Rarity
12.28ct True Face-Up is equivalent to that of a ~12.86 carat – 4.7% larger than the average

Analysis: A large Fancy Yellow Radiant cut with a very strong Inner-grade, bordering on “Intense,” featuring some colorless patches on the crown and without any green or brown Undertone. The face-up view of the diamond corresponds to that of a 12.86ct Radiant cut

High Auction Estimation: $9,893 pc
Price realized: $17,171 pc

Visual Assets:

Inner Grade..……………….4

Color Dispersion.………3

Undertone..…………………4

Total Visual Score….11 out of 12 

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Lot 1635

Description: 1.01 ct, Fancy Purple-Pink, Cushion, I1
GIA, Rarity, Diary
1.01ct True Face-Up is equivalent to that of a ~1.03 carat – 2.1% larger than the average

Analysis: A 1.01-carat Fancy Purple Pink cushion cut with a low Inner-grade. The warm Undertone creates a less attractive color sensation, and the I1 clarity limits its demand in the market. The larger face-up appearance gives the diamond a full representation of its carat weight.

High Auction Estimation: $76,727 total
Price realized: $48,660 Total

Visual Assets:

Inner Grade..……………….2

Color Dispersion.………3

Undertone..…………………2

Total Visual Score….7 out of 12

Quality Remark: I1 clarity

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Lot 1640

Description: 5.03 ct, Fancy Vivid Yellow, Radiant, VS2
GIA, Rarity, Diary
5.03 ct True Face-Up is Distinctly Smaller than Standard.

Analysis: A Vivid Yellow Radiant cut diamond with very high Color Dispersion and a pleasant orange Undertone. The Inner-grade appears to be on the lower side of the Vivid saturation spectrum. Please note that, according to the face-up algorithm, the diamond won’t represent its true carat weight.

High Auction Estimation: $76,269 pc
Price realized: Didn’t reach the minimum

Visual Assets:

Inner Grade..……………….2

Color Dispersion.………4+

Undertone..…………………4

Total Visual Score….10+ out of 12

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Lot 1680

Description: 13.79 ct, Fancy Yellow, Pear, VS2
GIA, Rarity, Diary
13.79ct True Face-Up is equivalent to that of a ~16.49ct – 19.6% larger than the average

Description: 13.52 ct, Fancy Yellow, Pear, VS2
GIA, Rarity, Diary
13.52ct True Face-Up is equivalent to that of a ~16.5 – 22.1% larger than the average

Analysis: Two large Fancy Yellow Pear-shaped diamonds with similar facet alignments present dark colorless patches on the crown. The Inner-grade is low; however, both diamonds have a larger face-up appearance in relation to their weight.

High Auction Estimation: $27,159 pc
Price realized: Didn’t reach the minimum

Visual Assets 13.79 ct:

Inner Grade..……………….2

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….8 out of 12

Visual Assets 13.52 ct:

Inner Grade..……………….1

Color Dispersion.………3

Undertone..…………………2

Total Visual Score….6 out of 12

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Lot 1682

Description: 4.01 ct, Fancy Intense Purplish Pink, Radiant, IF
GIA, Rarity, Diary
4.01 True Face-Up is equivalent to that of a ~4.5 carat – 14.0% larger than the average

Analysis: A 4.01-carat Fancy Intense Pink rounded corner square cut diamond with a low Inner-Grade. Despite its setting in a ring, large colorless triangle patches positioned at 12, 3, 6, and 9 o’clock are prominent, disrupting the overall color experience.

High Auction Estimation: $956,688 pc
Price realized: Didn’t reach the minimum

Visual Assets:

Inner Grade..……………….1

Color Dispersion.………2

Undertone..…………………3

Total Visual Score….6 out of 12

Quality Remark: Low Color Dispersion and Inner-Grade

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Lot 1690

Description: 14.51 ct, Fancy Yellow, Radiant, VVS1
GIA, Rarity, Diary
14.51ct True Face-Up is equivalent to that of a 19.26 – 32.7% larger than the average

Analysis: An elongated Radiant cut diamond features a typical facet alignment used by Alrosa during the beginning of this millennium. This cut, similar to one they applied to their colorless diamonds, accounts for the many colorless areas under the table. The absence of green or brown Undertones and the large face-up view offer significant potential for those aiming to improve diamonds by repolishing them. The GIA certification is dated 2011.

High Auction Estimation: $10,576 pc
Price realized: $12,856 pc

Visual Assets: 

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………4

Total Visual Score….9 out of 12

Quality Remark: Low Color Dispersion

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Lot 1700

Description: 2.46 ct, Fancy Light Pink, Pear, VS2
GIA, Rarity, Diary
2.46ct True Face-Up is equivalent to that of a ~2.49 carat – 1.2% larger than the average

Analysis: A Fancy light Pear shape diamond with some colorless patches on the crown and a pleasant Undertone.

High Auction Estimation: $166,345 pc
Price realized: Didn’t reach the minimum

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………3

Undertone..…………………3 

Total Visual Score….9 out of 12 

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Lot 1701

Description: 3.02 ct, Fancy Intense Blue-Green, Radiant, VS1
GIA, Rarity, Diary
3.02ct True Face-Up is Moderately below standard.

Analysis: A rare color combination of approximately 40% blue and 60% green in this relatively large Radiant cut diamond. Although the Inner-grade appears weak, this actually signifies a saturation level above average for diamonds with a green body color. The color is well-dispersed across the face-up.

High Auction Estimation: $211,718 pc
Price realized: $182,607 pc

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………4

Undertone..…………………3

Total Visual Score….10 out of 12

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Lot 1717

Description: 13.35 ct, Fancy Intense Yellow, Emerald, VVS2
GIA, Rarity, Diary
13.35 True Face-Up is equivalent to that of a ~14.4 carat – 8.1% larger than the average

Analysis: An Emerald cut diamond with a 1.05 ratio exhibits large colorless areas, inherent to this diamond shape with traditional facet alignment, and is graded for its dispersion accordingly. The Inner-grade is considered low for an ‘Intense’ classification.

High Auction Estimation: $28,737 pc
Price realized: $15,795 pc

Visual Assets:

Inner Grade..……………….2

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….8 out of 12

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Lot 1718

Description: 3.21 ct, Fancy Light Grey-Blue, Pear, VS1
GIA, Rarity, Diary 
3.21ct True Face-Up is equivalent to that of a ~4.06 carat-26.5% larger than the average

Description: 2.62 ct, Fancy Light Grey-Blue, Pear, VS2
GIA, Rarity, Diary
2.62ct True Face-Up is equivalent to that of a ~3.59 carat – 37.3% larger than the average Pear shape in this weight.

Analysis: Two Fancy Light Gray-Blue Pear-shaped diamonds feature an open culet and angles on the pavilion facets, suggesting this pair originates from the beginning of the last century and underwent a recut to enhance this saturation. The blue color sensation is slightly superior in the 2.62ct diamond, thereby receiving a higher Undertone grade.

High Auction Estimation: $239,023 pc
Price realized: Didn’t reach the minimum

Visual Assets 3.21 ct:

Inner Grade..……………….2

Color Dispersion.………2

Undertone..…………………2

Total Visual Score….6 out of 12

Visual Assets 2.62 ct:

Inner Grade..……………….2

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….8 out of 12

Quality Remark: Low visual assets

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Lot 1747

Description: 10.33 ct, Fancy Intense Orangy Pink, Heart, VVS1
GIA, Rarity, Diary
10.33 ct True Face-Up is equivalent to that of an ~11.74 – 13.7% larger than the average

Analysis: A 10.33-carat Fancy Intense Orangy Pink with a very low Inner-grade, bordering on a grade below. The color mosaic is perfectly dispersed across the face-up view, and the color sensation aligns well with the description in the report. The face-up appearance is significantly larger, commanding a premium.

High Auction Estimation: $495,169 pc
Price realized: Didn’t reach the minimum

 

Visual Assets:

Inner Grade..………….…….1

Color Dispersion.………4+

Undertone..…………………3

Total Visual Score….8 out of 12

Quality Remark: Low Inner-Grade

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Lot 1748

Description: 66.44 ct, Fancy Intense Yellow, Cushion, VS2
GIA, Rarity, Diary
66.44ct True Face-Up is Distinctly Smaller than Standard.

Analysis: A very large Fancy Intense Yellow cushion cut diamond exhibits perfect Color Dispersion, creating a pleasant and even color mosaic across the face-up view, with no green or brown Undertone visible in the hue. However, the face-up appearance corresponds to that of a smaller carat weight.

High Auction Estimation: $23,097 pc
Price realized: $22,264 pc

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………4+

Undertone..…………………4

Total Visual Score….11+ out of 12

Quality Remark: Appears smaller

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Lot 1773

Description: 7.01 ct, Fancy Vivid Yellowish Orange, Cushion, VS2
GIA, Rarity, Diary
7.01ct True Face-Up is equivalent to that of an ~8.7 carat – 24.5% larger than the average

Analysis: With only approximately 20% yellow in the mix, this diamond appears predominantly orange and exhibits high visual assets. It possesses a strong Inner-grade, creating a vivid and a pleasant orange sensation that exceeds expectations set by the report. Although the crown is not entirely colorless, it shows a much lower saturation compared to the color under the table, a factor that impacts the dispersion grade. The face-up appearance is significantly larger relative to its weight, commanding a considerable premium in price.

Price realized: $537,277 pc

Visual Assets:

Inner Grade..……………….4

Color Dispersion.………3

Undertone..…………………4

Total Visual Score….11 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.