Talking about rarity in jewelry: 38-carat Golconda diamond necklace, designed by Jacques Timey for Harry Winston

The rarest 38.00-carat Golconda diamond necklace, designed by Jacques Timey for Harry Winston, in addition to its unique characteristics, has a history that made it an outstanding example among jewelry of the highest class. This combination of origin, stones' properties, design, ownership history and famous Jewelry House touch makes it outstanding example of one-of-a-kind jewelry piece.

This luxurious jewelry previously belonged to the famous Christina Onassis, the heiress of the second husband of Jacqueline Kennedy, Greek billionaire Aristotle Onassis.
Harry Winston's Pear-Shape Golconda Diamond Necklace
Famous Golconda mine in India is the origin of the unique stones, including the Orlov, Koh-i-noor and Hope diamonds.Golconda diamonds are the purest of all and have unparalleled characteristics. They are recognized as the best in the world and the diamond in this necklace is a living proof of that.
Whiter than white…
The center diamond in this incredible necklace is one of the finest diamonds available on the market today. It is certified by the Gemological Institute of America (GIA) as a D color and Type IIa, meaning that this gemstone is completely colorless and a full two shades whiter than the whitest D color diamond.
This is possible due to the complete absence of nitrogen, which gives diamonds their color. This gemstone is one of the brightest and whitest diamonds known. It also exhibits VVS1 purity, which means that its wonderful color is not marred by any imperfections. Only 1-2% of diamonds can boast such characteristics and are called lla diamonds.
Harry. Winston's Pear-Shaped Goldconda Diamond Necklace

Harry Winston's magic

The legend of the jewelry industry, Harry Winston, ensured that the necklace matched the perfect diamond.
Responsible for this task, jewelry designer Jacques Timey perfectly combines the timeless aesthetic with the glamorous shine for which Harry Winston's creations are renowned.
Crafted in white gold and platinum, this necklace features 25 carats of perfectly matched G color and VS clarity marquise-cut diamonds, making it absolutely dazzling.
Finding a stone of this quality weighing more than a few carats is rare, but finding a stone weighing 38.00 carats - especially in a necklace from Harry Winston - is truly a once in a lifetime, because mining in Golconda closed hundreds of years ago!
This necklace has a great history of origin, which is always reflected in the value of high-end jewelry and attracts additional attention. It once belonged to entrepreneur, socialite and billionaire heiress Christina Onassis. It was a gift from her father, Aristotle Onassis, husband of Jacqueline Kennedy Onassis, for whom Harry Winston also designed jewelry.
Born into a world of luxury and style, Christina was known for her extravagant haute couture jewelry collection, in which this necklace became a real gem.
Christina Onasis Jewelry
The Harry Winston House is renowned for its dramatic and ultra elegant design. One of the most respected names in the world of luxury jewelry, Harry Winston, known today as the "King of Diamonds", first opened the store in 1932 and continues to create eye-catching jewelry for celebrities and discerning clients around the world. His clientele include royal family members and celebrities, from the Duke and Duchess of Windsor to Jackie Kennedy and from Marilyn Monroe to Elizabeth Taylor. His pieces are synonymous with uncompromising quality and unparalleled glamour.
Stamped with French assay marks for platinum and 18K white gold and with maker's mark for Jacques Timey.
On June 12, 2008, at a London Christie's auction dedicated to the Onassis family's jewelry collection, the necklace sold for $186,000 per carat. The buyer purchased it for $7.1 million, more than doubling expectations.
Today's starting price of this treasure is 7.5 million dollars. 
Reference:
Cf. Laurence Krashes, Harry Winston, The Ultimate Jeweler, New York, 1986