Pre-Auction Analysis: January 31st, Sotheby’s Hong Kong

Our Sotheby’s Important 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 250

Description: 7.67 ct, Fancy Yellow, Brilliant, VVSI Rarity, GIA, Diary Report

Analysis: 

A round brilliant cut diamond, likely manufactured during the 1970s-1980s, features a large table and low depth, along with typical low dispersion. At the time of its polishing, these diamonds were considered to be of low color (Cape). Observing at a 45° angle from the table facet, it is possible to appreciate the color potential of the diamond had it been polished into a modified shape.

High Auction Estimation: $26,445 pc

Price realized: Didn’t reach the minimum

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………4

Total Visual Score….8 out of 12

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Lot 296

Description: 14.51 ct, Fancy Intense Yellow, Cushion, VS1 Rarity, GIA, Diary Report

Analysis: 

A fancy intense yellow cushion cut surrounded by a large colorless frame around the table. The inner-grade is strong, and no green or brown undertone is present in the hue. According to the True Face-Up in the Diary Report, this cushion appears true to its weight, an important feature to consider when buying a fancy color diamond.

High Auction Estimation: $26,445 pc

Price realized: $22,390 pc

Visual Assets:

Inner Grade..……………….4

Color Dispersion.………3

Undertone..…………………4

Total Visual Score….11 out of 12

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Lot 297

Description: 3.06 ct, Fancy Pink-Purple, Pear, VS2 Rarity, GIA, Diary Report

Analysis: Didn’t reach the minimum

A purple color diamond with approximately 40% pink as a modifier. This diamond is cut and polished similarly to a colorless diamond, leaving a large colorless area in the shape’s center. The inner grade is weak, bordering on fancy light. Overall, the color sensation is pleasant. 

High Auction Estimation: $208,999 pc

Price realized: Didn’t reach the minimum

Visual Assets:

Inner Grade..…………….….1

Color Dispersion.………2

Undertone..…………………4

Total Visual Score….7 out of 12

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Lot 361

Description: 21.38 ct, Fancy Vivid Yellow, Radiant, VS1 Rarity, GIA, Diary Report

Analysis: A large vivid yellow radiant cut diamond features a low inner grade and prominent colorless patches around the crown area. No significant green or brown undertone is visible in the hue. According to the True Face-Up data in the Diary Report, this radiant looks slightly larger in relation to its weight, an important feature to consider when buying color diamonds.

High Auction Estimation: $65,808 pc

Price realized: Withdrawn from auction.

Visual Assets:

Inner Grade..…………….….1

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….7 out of 12

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General

We use 1, 2, 3, 4, and 4+ to grade the three visual elements that GIA is silent about, although they impact the value dramatically.

Inner-Grade refers to the strength of color within each GIA saturation category:

Grade 1 weakest, bordering the saturation below.

Grade 2 weak (most common).

Grade 3 full-bodied color (above average).

Grade 4 very strong saturation.

Grade 4+ applies to the vivid category only, exhibiting the strongest possible saturation (rarely seen).

Undertone refers to a subtle hue influence in the body color of the diamond.

For example:

A Fancy Blue Diamond with a significant gray presence in its general appearance will be graded with a low undertone grade of 1. A Fancy Blue that has no gray influence that is close to a primary blue will receive the grade, 4.

In a Pink Fancy Color Diamond, a diamond with a warm undertone (such as orange or brown) will receive a low undertone grade. A pink diamond with a cold undertone (such as purple) will receive a high grade.

In Yellow Fancy Color Diamonds, low foreign influence or a light orange influence will grant the diamond a high undertone grade. When the yellow undertone looks like a true primary yellow, it will receive the rare grade 4+. Green and brown undertones will grant a low grade in the yellow category.

Color Dispersion relates to how well the color is dispersed in the face-up view of a Fancy Color Diamond, regardless as to whether the GIA grades the diamond as even. A diamond with many colorless areas will receive the grade 1, while a diamond that exhibits its face-up view with no colorless patches will receive the grade 4+. Unlike the first two elements, the color dispersion is not a gemological quality and is the result of cutter proficiency.