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Pre-Auction Analysis: February 3, 2023, Sotheby’s HK

By FCRF Team | 01.02.23
Pre-Auction Analysis: February 3, 2023, Sotheby’s HK

Important Jewels

Pre-Auction Analysis: February 3, 2023, Sotheby’s Hong Kong, Important Jewels

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 stones with exceptional characteristics. Stones 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.
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: 222

Description: 5.08 ct, Fancy Intense Yellow, Marquise, VS1 

High Auction Estimation: $20,135 pc

Price realized: $20,712 pc

GIA Report: View

Analysis: 

A 5 carat Fancy Intense Yellow Marquise with high color dispersion and a strong Inner-Grade. No significant undertone is seen in the hue.

*General Remark:  Fancy color diamonds are rarely seen in a marquise cut and are perceived as exotic. However, this shape saw its heyday in the 1970s, and current demand for it is not very high. Therefore, the price this shape achieves may not always reflect its rarity and charm.

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………4

Undertone..…………………3

Total Visual Score….10 out of 12

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Lot: 233

Description: 8.14 ct, Fancy Intense Yellow, Radiant, VS1 

Description: 8.04 ct, Fancy Intense Yellow, Radiant, VVS2 

High Auction Estimation: $ 30,028 pc

Price realized: $23,010 pc

Rarity 8.14: 10-13 diamonds yearly – Share this rarity result – Here

Rarity 8.04: 9-12 diamonds yearly – Share this rarity result – Here 

GIA Report 8.14: View

GIA Report 8.04: View

Analysis:

Two Radiant-cut diamonds with similar weights and dimensions. There is a significant discrepancy in table size between the two diamonds (72% vs 63%), an important factor that reduces their compatibility as a matching pair. Considering their facet alignment and the large colorless patches, it is reasonable to assume they were cut and modified from what used to be round brilliant stones with a lighter saturation.

Visual Assets 8.14:

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………3

Total Average Score….8 out of 12

Visual Assets 8.04:

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………3

Total Average Score….8 out of 12

Quality remark: low dispersion and low comparability.

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Lot: 254 

Description: 10.02 ct, Fancy Brownish Yellow, Emerald, VS2  

High Auction Estimation: $15,312 pc

Didn’t reach the minimum

GIA Report: View

Analysis:

Visual Assets:

A Yellow Emerald-cut diamond with a ~15% brown modifier in its color. The brown addition makes the color appear stronger and the color dispersion is quite high for a step-cut. The stone’s depth is 71%.

Inner Grade..……………….4

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….10 out of 12

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Lot: 262 

Description: 8.88 ct, Faint Pink, Radiant, IF

High Auction Estimation: $69,112 pc

Price realized: $65,624 pc

Rarity: 5-6 diamonds yearly – Share this rarity result – Here 

GIA Report: View

Analysis:

An 8.88 carat Faint Pink Radiant-cut diamond. For those who wonder why a stone found at the lower end of the GIA color scale appears so saturated, the answer lies in the pink coating covering the inside of the gold cup in which the stone is mounted. This is a well-known technique to enhance diamonds with a low color grade.

Because the (external) pink influence is extremely strong, we were unable to responsibly assess the diamond’s visual assets.

A remark about a comment of “Not Applicable”:  Most diamonds with a faint color grade receive this comment because their weak color becomes elusive as it blends with the colorless reflections. This prevents them from receiving a proper distribution grade on the GIA report.

Visual Assets:

Inner Grade..……………….N/A

Color Dispersion.………N/A

Undertone..…………………N/A

Total Visual Score…. N/A

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Lot: 265

Description: 13.03 ct, Fancy Intense Yellow, Emerald, VS1

High Auction Estimation: $39,250 pc

Price realized: $32,299 pc

Rarity: 1-3 diamonds yearly – Share this rarity result – Here 

GIA Report: View

Analysis: 

A 13 carat Fancy Intense Yellow Emerald-cut diamond with a very strong Inner-Grade, bordering on a vivid, with a pleasant undertone. The color is reflected only through the four corners of the pavilion, creating a pronounced yellow X shape when looking at the face-up of the stone, while all other areas remain colorless.

The face-up surface appears large in relation to its carat weight.

Visual Assets:

Inner Grade..……………….4

Color Dispersion.………2

Undertone..…………………3

Total Visual Score….9 out of 12

Quality remark: low color dispersion

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Lot: 274

Description: 15.05 ct, Fancy Intense Yellow, Oval, SI1  

High Auction Estimation: $29,734 pc

Price realized: $27,964 pc

Rarity: Once every 1-2 years – Share this rarity result – Here 

GIA Report: View

Analysis:

A large Fancy Intense Yellow Oval, SI1 clarity, with very high visual assets. Although the stone has a small table facet (48%), this doesn’t affect its overall face-up appearance.

Visual Assets:

Inner Grade..……………….4

Color Dispersion.………4

Undertone..…………………4

Total Visual Score….12 out of 12

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Lot: 289

Description: 7.01 ct, Fancy Vivid Yellow, Emerald, VVS2 

High Auction Estimation: $ 43,774 pc

Price realized: $41,562

Rarity: 3-7 diamonds yearly – Share this rarity result – Here 

GIA Report: View

Analysis:

A rectangular Vivid Yellow Emerald-cut diamond exhibiting a strong Inner-Grade despite the strong blue fluorescence. The facet alignment of the stone was made without any modification to improve color dispersion, and as such, the vast majority of the face-up view is colorless.

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………3

Total Visual Score….8 out of 12

Quality remark: low color dispersion, strong blue fluorescence. 

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Lot: 292

Description: 3.67 ct, Fancy Blue, Cushion, VS2 

High Auction Estimation: $383,225 pc

Didn’t reach the minimum

Rarity: Once every 5-6 years – Share this rarity result – Here 

GIA Report: View

Analysis:

A 3.67 Fancy Blue Cushion shape with excellent color dispersion but low Inner-Grade. Looking at the soft green undertone, it’s reasonable to assume the stone is not a typical Type IIb Blue diamond.

Visual Assets:

Inner Grade..……………….2

Color Dispersion.………4

Undertone..…………………3

Total Visual Score….9 out of 12

Quality remark: low inner grade

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Lot: 294

Description: 33.03 ct, Fancy Yellow, Oval, VS2  

High Auction Estimation: $18,580 pc

Price realized: $18,132

Rarity: Once every 1-2 years – Share this rarity result – Here 

GIA Report: View

Analysis:

A very large Fancy Yellow Oval-cut diamond with two large colorless areas on the crown. Savvy buyers may think that its short ratio (1 x 1.32) does not correspond with a classic oval shape.  The Inner-Grade is strong, and no significant green or brown undertone is seen in the color.

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………3

Undertone..…………………3

Total Visual Score….9 out of 12

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Lot: 307

Description: 5.55 ct, Fancy Light Blue, Radiant, IF

High Auction Estimation: $ 195,806 pc

Didn’t reach the minimum

Rarity: Once every 5-6 years – Share this rarity result – Here 

GIA Report: View

Analysis:

A fancy Light Blue Radiant-cut diamond with a symbolic carat weight of 5.55.

The facet alignment seems typical of the late 1990s. The diamond presents a small colorless culet with two colorless triangles visible through the crown. The unusual facet alignment on the GIA plot clearly shows it.

The diamond is embedded in a closed gold cup, and chances are that the inside of the cup is coated with a blue material to artificially reinforce its Inner-Grade. We ask that you take our visual analysis with prudence.

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………3

Undertone..…………………4

Total Visual Score….10 out of 12

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Lot: 308

Description: 5.30 ct, Fancy Light Pink, Pear, VS2 

High Auction Estimation: $ 180,919 pc

Didn’t reach the minimum

Rarity: 1-3 diamonds yearly – Share this rarity result – Here 

GIA Report: View

Analysis:

Visual Assets:

A 5.30 carat Fancy Light Pink Pear shape. The stone is mounted in a dark pink gold cup that is clearly visible through the various facets around the face-up of the stone. In this case, as well, we were unable to analyze the visual assets responsibly due to this manipulation.

Inner Grade..……………….N/A

Color Dispersion.………N/A

Undertone..…………………N/A

Total Visual Score….N/A 

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Lot: 317

Description: 8.08 ct, Fancy Vivid Yellow, Emerald, VS2 

High Auction Estimation: $ 80,702 pc

Didn’t reach the minimum

Rarity: 4-8 diamonds yearly – Share this rarity result – Here 

GIA Report: View

Analysis:

An 8.08 carat Emerald-cut diamond that was cut and polished like a colorless diamond. Although its Inner-Grade is strong, most of the diamond’s face-up is colorless due to its large, glassy facets. A green undertone is present in its hue.

Visual Assets:

Inner Grade..……………….3

Color Dispersion.………2

Undertone..…………………2

Total Visual Score….7 out of 12

Quality remark: low color dispersion, green undertone.

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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 stone.

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 stone with a warm undertone (such as orange or brown) will receive a low undertone grade. A pink stone 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 stone 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 stone as even. A stone with many colorless areas will receive the grade 1, while a stone 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.

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