In this pre-auction report, we will focus on visual elements of some rare and unusual fancy color diamonds. We will also try to give you some interesting 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 any remark next to the grade, 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 X – no filters were applied.

All auction valuations are per carat and in US Dollars.

Sotheby’s Auction – May 15th, 2018

Lot #374

2.63 carat fancy vivid purplish pink round modified brilliant cut, SI1

High catalog estimation: $1,138,684 per carat

It’s well known that round fancy color brilliant cut diamonds achieve the highest price per carat. The reason for that lies in the fact that there is very little one can do in order to concentrate the color and spread it evenly around the face up of the stone. In this case, whoever cut this 2.63-carat stone made a good job reinforcing the color within the limitations of a round shape and achieving the vivid grade. Unfortunately the stone cannot achieve the full premium for the shape simply because the bottom is modified and the depth percentage is 75. This is an extremely unusual depth for any fancy color diamond, nevertheless for a round. ...