Our Pre-Auction analysis focuses on 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 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 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.


Lot #1892

5.00 carat fancy vivid blue Emerald Cut, VS2

High catalog estimation: $3,057,600 per carat


The ultimate test for a ‘Vivid’ is whether you recognize its lively and lucid detailed colorful nature, without doubting if it’s actually vivid or not or look at the GIA report for reassurance.
In this case, a second look at the report is definitely needed. This blue diamond is...