In this pre-auction analysis, we have a relatively large amount of blue fancy color diamonds. Most of them seem to be coming from the secondhand market as almost no new blue rough have been unearthed in the last few years. As always, we will focus on visual elements and other observations that are not expressed on the GIA report nor in the catalog.

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


For your convenience we have added direct links for the GIA reports and some FCRF Rarity reports.

All images in this article review were taken with an iPhone 7 – no filters were applied.

All auction valuations are per carat and in US Dollars.


Christie’s Auction – April 17th, 2018


Lot #71

40.57 carat fancy intense yellow cushion cut, VS2

High catalog estimation: $29,579 per carat

Price Realized: $23,971 per carat

A cushion cut diamond that was cut without giving too much attention to the color dispersion and was left with a large colorless frame. The yellow undertone has no green or brown influence. The “Intense” inner-grade is above average, and the VS2 clarity grade is a result of a black crystal underneath the table facet. ...