The extremely rare, 10-carat Mediterranean Blue diamond could fetch a whopping $20 million at Sotheby's High Jewelry auction on May 13.

The intrinsic value of jewelry is ... Among them: a high-profile previous owner (the Taylor-Burton diamond); a specific geographic origin (velvety-blue Kashmir sapphires); even the rough from ...

and Blue Book Collection brooch in yellow gold with pink and yellow sapphires, an emerald and diamonds BVLGARI High Jewelry necklace in platinum with one antique cushion ruby, one pear diamond ...