Rare 25ct. Diamond to Lead Christie’s Geneva

Jonker Diamond

A storied diamond connected to the Oppenheimer family will be among the top lots at next month’s Geneva auction at Christie’s, with a presale estimate of $2.5 million to $3.5 million.

The rectangular cut, 25.27 carat, D color Jonker V ring will go under the hammer at the Magnificent Jewels sale on May 15, the auction house said last week.

The stone was cut from a 726 carat rough South African farmer Johannes Jacobus Jonker discovered in 1934. At the time, the Jonker was the fourth largest gem quality diamond ever unearthed.

A subsidiary belonging to Sir Ernest Oppenheimer, the founder of Anglo American and a former De Beers chairman, bought the polished stone. In 1935, Harry Winston purchased the diamond and set it in a ring. Later that year, it was displayed during the Silver Jubilee celebrations for King George V and Queen Mary.

Christie’s will also offer a heart shaped, fancy deep blue diamond ring, featuring two stones weighing 2.22 carats and 2 carats, valued at $3.5 million to $4.5 million. Separately, an old cushion-cut, 118.05 carat, fancy yellow diamond carries an estimate of $2.5 million to $3.5 million.

Other notable lots are a necklace comprising 110 natural pearls with a presale estimate of $2.5 million to $3.5 million, and a pear shaped, 75.61 carat emerald pendant necklace expected to fetch $2 million to $3 million.

In addition, the Geneva sale will feature an early 19th century emerald and diamond fringe necklace Henri d’Orléans, duke of Aumale, gave to his goddaughter, Princess Hélène of France, for her 1895 wedding to Prince Emanuele Filiberto of Italy.

Source: Diamonds.net

Diamond cleaning

Because your diamond when worn naturally attracts grease or oil, they will need periodic cleaning.

Even when touching a diamond with your fingers natural oils from your skin will change the brilliance of your diamond, making your diamond lose its lustre or brilliance.

A simple way to keep your diamond jewellery looking beautiful is a weekly bath in a household cleaning solution. A simple window cleaner will work. But make sure you give it a thorough rinsing followed by a very light brushing using an old tooth brush to remove the oils and cleaning liquid.

Pay special attention to the underside of the ring and bottom of the stone, as this is where most of the oils or hand creams accumulate.

Make sure when using a brush not to apply to much pressure especially if the jewellery is old or fragile. This is a good time to check the diamonds are tightly set and none are missing.

Never use Chlorine, bleaches or abrasives when cleaning diamonds set in jewellery. This will remove the rhodium plating on white gold and could leave scratches which will attract even more dirt.

If the ring has fine claws or filigree work an ultrasonic cleaner is necessary to remove deep encrusted dirt behind the diamonds. High frequency sound waves and jewellery detergent fluid will remove hard to get to dirt and grime. Make sure this is done by a professional to avoid damage or loss of stones.

Brown Diamond

In natural diamond the colour is related to a lattice imperfection. This can be mimicked in synthetic or treated diamond by a variety of treatments including annealing, heating or irradiating. The heat and pressure or irradiation can result in the lattice deviation resulting in the brown or pink colour.

Orange Diamond

The ultimate colour for the collector, Orange is extremely rare in diamond. To be certified fancy orange colour, there cannot be any brown in the stone.

Polish Lines

Lines left on the surface of the diamond which are visible under magnification, normally removed during the final diamond polishing process. Polish lines can affect the polish grade of the diamond.

Seal

Plastic covering that provides a safeguard against loose diamonds being lost or damaged. Laboratory sealing has a number of security features including electrostatic security bars, pressure-sensitive transparent adhesive and cryptoprint text which only becomes visible after opening the seal.

Diameter

Diameter is a reference measurement against which most of the proportions on a diamond are calculated. On a round brilliant cut diamond, this is the length in millimeters of a straight line going through the center of a diamond. Click here to learn which standard diameter measurements correspond to specific well-proportioned carat weights. On a fancy shaped diamond, this is the average measurement in millimeters of the length and width.