Pre-Auction Analysis: April 19th 2016, Sotheby’s New York

Our pre-auction analyses focus on visual elements that are not expressed on the GIA report, such as “inner-grade”, “undertone” and “color dispersion”. We use grades 1, 2, 3, 4 and 4+ to evaluate these features. It is often difficult to identify these characteristics when viewing stones in an auction catalogue. For the first time, the foundation is including the auction house premium, which reflects the actual price the buyer will pay based on the high estimate, price per carat.

Lot #189

12.45 carat, Fancy Purplish Pink, Cushion, VS2 

High catalog estimation: $430,000 per carat
Price Realized: 366,426$ pc

The undertone of this Fancy Purplish Pink diamond is not as sweet when viewed in person, but the main discrepancy between the stone and the catalogue is the color dispersion, which is not accurately portrayed (3). This stone has an above average inner grade (3).

Lot #311

30.81 carat, Fancy Vivid Yellow, Pear, VS2 

High catalog estimation:  $50,000 price per carat
Price Realized Per Carat- Didn’t reach the minimum (Updated 21/4/16)

This large Fancy Vivid Yellow pear-shaped diamond has a sufficient inner grade (3), an average undertone for a yellow (3), and very good color dispersion (4). Though the stone is not as impressive in person as it appears in the catalogue, the differences are not very distinct. When viewed in natural light, it is quite obvious that the stone has blue fluorescence.

This diamond’s relatively low price per carat is a result of two elements: high depth percentage and strong fluorescence. The stone has a 70.7% depth percentage, which, for a pear shape, is very deep. It also has a very strong blue fluorescence, which is not mentioned in the catalogue description.

Lot #319

9.54 carat, Fancy Deep Blue, Cushion, VVS2

High catalog estimation: $4,050,000 price per carat
Price Realized Per Carat- Didn’t reach the minimum (Updated 21/4/16)

In the catalogue, the image of this stone resembles a Vivid Blue, but in person the stone is more of a classic, Deep Blue. Many Deep Blue stones have a tendency to appear very dark to the point where their actual color is not visible, but this stone’s blue hue is very apparent. Though its color is deep, it is a nice stone and conveys the feeling that you have a blue diamond in your hand. According to the GIA’s plot on the report, the stone could likely be re-cut to an Internally Flawless grade.