Our Pre-Auction analysis focuses on some unusual elements that are hidden from the unprofessional eye and 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 below).

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 most suitable for high-end jewelry, collectors, and the investment community. A detailed explanation of our grading system is at the bottom of this article.

For your convenience, we have added direct links for 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.

Christie’s Hong Kong Magnificent Jewels, May 29th, 2018


Lot #2093

8.01 carat fancy vivid blue pear shape, IF

High catalog estimation: $3,084,628 per carat

An elongated vivid blue pear shape with no gray undertone and a below average inner-grade in its category. Diamonds with low depth percentage usually achieve a premium for their relatively large look. However, in fancy color diamonds, low depth percentage might jeopardize the color dispersion, as we see in this stone. Tilting the stone gently reveals interchanging “see-through”  areas on the rounded side. The round brilliant diamond on the top has a very strong inner-grade, good color dispersion, and undertone. It is a modified round brilliant with a large visible feather on the table. 

Vivid blue pear shape

Inner-Grade Color Dispersion Undertone
2 3 4

Total quality score: 9

Lot #2093

To review the GIA Report Click here 


Lot #1904

10.04 carat fancy vivid yellow cushion-shaped, VS2

High catalog estimation: $101,972 per carat

A vivid yellow cushion cut diamond with a very good color dispersion and a clear yellow undertone. The cushion has a very high depth percentage (76.6%), which creates a small face-up appearance in relation to its weight.

When looking at the comments on the GIA report, you will see an indication of a laser inscription of the word ‘Zimi’ (should be spelled ‘Zimmi’), apparently to give the illusion that the stone was unearthed in Sierra Leone in order to grant the stone the ‘allure’ of an exceptional vivid yellow unearthed next to the Zimmi village. Unfortunately, this stone ...