Tuesday, October 21, 2008

Sotheby's Auction - Yellow Diamond Ring

Sotheby's is holding an auction on Nov 6, 2008.  The ring shown above stood out among the various pieces.  The proceeds of the sale of this yellow diamond, daffodil ring made by George Pragnell will go to the Marie Curie Cancer Care charity.  Sotheby's provides a good description on colored diamonds:

"Fancy coloured diamonds are graded based on two factors. The first is their basic hue, such as pink, yellow, blue and even green, it is interesting to note that a secondary undertone that enhances the colour of a diamond is considered a plus, while a secondary undertone that detracts from the colour is thought to be a negative. The second is their intensity of colour. Both colour characteristics form the basis for determining a fancy coloured diamond's rarity and value.

When grading fancy coloured yellow diamonds, the Gemological Institute of America, G.I.A uses the following categories:

1. Fancy Light
2. Fancy
3. Fancy Intense
4. Fancy Dark
5. Fancy Deep
6. Fancy Vivid

Unlike other coloured diamonds (except brown) yellow diamonds with grades of Faint, Very Light and Light are not considered to be fancy-coloured diamonds, but are part of GIA's D-Z colour grading scale.

The formation of white diamonds involves a process that requires the presence of carbon being crystalised under immense heat and pressure deep in the earth's crust, but to colour a diamond one also needs the presence of additional trace elements and distortions to the typical diamond crystal. If an element interacts with carbon atoms during a diamond's creation, the diamond's colour can change. Radiation and pressure on a diamond's structure will also impact its colour as well. The presence of nitrogen can impart yellow or orange shades to a diamond."

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