Pre-Auction Analysis: November 15th 2018, Sotheby’s Geneva, Magnificent Jewels

Our Pre-Auction Analysis focuses on elements that are hidden from the non-professional eye. As always, we will describe the important visual elements for those who cannot attend the preview. We will discuss characteristics such as Undertone, Color Dispersion, and Inner-Grade (UDI; a detailed explanation appears at the bottom of this article).

We use grades 1, 2, 3, and 4 (1 being the lowest grade). The grade 4+ is granted in rare cases and stands for an exceptional characteristic. Stones that receive a minimum total UDI score of 8, without a remark, are considered to be “gems” and are mostly suitable for high-end jewelry, collectors and the investment community.

For your convenience, we have added direct links to the GIA reports.

• All images in this article review were taken with an iPhone 10. No filters were applied.
• All auction valuations are per carat and in US Dollars.

Sotheby’s, Geneva Magnificent Jewels, November 15th 2018

Lot #570

2.61 carat fancy vivid blue pear shape, VS2

3.06 carat fancy vivid blue pear shape, VS2

High catalog estimation: $1,773,860 per carat

Unsold – Didn’t reach the minimum

Two vivid blue pear shapes with 73% and 82% depth, respectively. Each has an extremely thick girdle on various sides, appearing no bigger than 2 carats.

The 2.61 has a minor gray undertone and a lower inner-grade:

Total quality score: 9 (high-depth percentage, with a small appearance)

The 3.06 has no gray undertone, exhibiting a primary blue hue:

Total quality score: 11 (high-depth percentage, with a small appearance)

To review the GIA Report Click here (11890077)

To review the GIA Report Click here (11993126)

Lot #567

21.19 carat fancy light pink cushion shape, VVS2

High catalog estimation: $308,617 per carat

Realized Price: $349,601 per carat

A very shallow old mine cushion that was cut during the previous century but went through a “cosmetic” polishing process. This diamond has a low color dispersion, which affects the inner-grade as well.

Total quality score: 8

To review the GIA Report Click here (1152036418)

Lot #566

5.04 carat fancy vivid blue cut-cornered rectangular shape, SI1

High catalog estimation: $2,397,930 per carat

Unsold – Didn’t reach the minimum

A vivid blue radiant cut with no gray undertone, exhibiting a clear primary blue hue. The SI1 clarity is a result of two black crystals under the crown that are invisible to the naked eye. A few colorless patches appear around the crown area.

Total quality score: 10

To review the GIA Report Click here (1142945155)

Lot #557

7.37 carat fancy intense orangey pink step cut, VS1

High catalog estimation: $573,666 per carat

Unsold – Didn’t reach the minimum

An Emerald cut diamond with low color dispersion, even for a step cut. The orange modifier leans towards a warm brown hue, and the graining reduces the translucency and sparkle.

Total quality score: 6

To review the GIA Report Click here (6197058597)

Lot #551

2.00 carat fancy deep bluish green cushion shape, SI1

High catalog estimation: $907,432 per carat

Realized Price: $931,678 per carat

A very rare color combination with a very good undertone. A large “natural” is located in one of the corners of the pavilion, but it is well hidden under one of the prongs. Due to the high depth percentage, the stone appears smaller than its actual carat size.

Total quality score: 11

To review the GIA Report Click here (17493168)

Lot #548

2.02 carat fancy intense blue brilliant cut, IF

High catalog estimation: $1,495,739 per carat

Realized Price: $1,660,416 per carat

A round brilliant cut with a large table (69%), a feature that is quite common in fancy color round stones. The color inner-grade is very strong, bordering on a Vivid, and the undertone has almost no traces of gray.

Total quality score: 10

To review the GIA Report Click here (1192504230)

Lot #421

20.03 carat fancy intense yellow brilliant cut, VVS1

High catalog estimation: $22,778 per carat

Realized Price: $19,796 per carat

A diamond that was modified from a round brilliant cut in order to reinforce its saturation. Some of the original facets of the round brilliant are still seen among the more recent ones. The color dispersion is low, with many colorless patches around the crown angle. The inner-grade and the undertone are average.

Total quality score: 8 (low color dispersion).

To review the GIA Report Click here (17219866)

General

We use 1, 2, 3, 4, and 4+ to grade the three visual elements that GIA is silent about, however, 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 abounded).

Grade 3 full-bodied color (above average).

Grade 4 very strong saturation.

Grade 4+ applies for 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 and will be 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 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 has only to do with cutter proficiency.