Pre-Auction Analysis: 2016, Sotheby’s Hong Kong

Our pre-auction analysis focuses on visual elements that are not expressed on the GIA report, such as “inner-grade”, “undertone” and “color dispersion”. We use simple grades 1, 2, 3, 4 and 4+ to evaluate these features. It is often difficult to identify such characteristics when viewing stones in an auction catalogue.

We are delighted to see that our readers are embracing the 1-4+ grading system.

This pre-auction analysis focuses on two important items from the upcoming Sotheby’s sale in Hong-Kong. Please note that all photos were taken with an iPhone 6.

Lot 1704 10.81 carat fancy vivid yellow oval, vs2.

Catalog estimate:  $100,000 to $140,000 per carat

It is not very common to see large vivid yellow diamonds in an oval shape. According to the Rarity Evaluator, oval shape diamonds represent approximately 8% out of all the yellow fancy color category. Only 1-5 new stones with similar characteristics come to the market every year. The stone has an inner-grade of 3, which is above average. When looking at the catalog image, one might think the color dispersion is perfect, with no colorless patches. In reality, the stone has two large black patches on each side and receives a grade of 3.

Although the undertone of the stone is not a clear “primary yellow” and leans towards a warm yellow, it is quite attractive and receives the grade 3 as well.

Lot 1794 6.59 carat Fancy intense purple pink pear shape internally flawless.

Catalog estimate:  $800,000 to $980,000 per carat

This pink pear shape diamond has a distinct presence of purple in its color composition. When a pink diamond color leans towards the “cooler” part of the spectrum, in the professional G’argon, it is referred to as “sweet” and thus will receive a high undertone grade – 4 in this case. The inner-grade is 2 which is below the average. When it comes to the color dispersion, the catalog, again, presents a falls description. The stone has noticeable areas with black and white patches and receives a grade of 3 (out of the mounting it may receive a lower grade).

According to our Rarity Evaluator this rare diamond receives a “One of-a-kind” grade. New pink (or purple pink) diamonds in the intense grade above 5 carat come into the market once every few years. Internally flawless pink diamonds represent 7% of all pink diamonds.