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). Grade 4+ is granted in rare cases and stands for stones with 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, NY Magnificent Jewels, December 4th 2018

Lot #98

10.62 carat Fancy Vivid Blue Pear shape, VVS1

High catalog estimation: $2,824,859 per carat

A large vivid blue pear shape with very good visual characteristics. Two visible colorless areas are situated on each side of the stone, and no ...