On May 14th and 15th Sotheby's Geneva will auction the famous Beau Sancy Diamond. The 34.98 carat diamond is the property of the Royal House of Prussia, with provenance dating back to Marie de Medici. The auction estimate is $2-4 million dollars. It is a beautiful old cut and I can't wait to see what it goes for!
Here is a photo of her Royal Highness wearing the Beau Sancy as the focal point of the tiara at her coronation in 1610.
The media keeps stating that the diamond is 400 years old. What they really mean is that it was cut 400 years ago. Diamonds were formed in the earth's mantle billions of years ago.
In any case it is a real beauty. You must take a look at this gorgeous sparkler in motion on youtube.