Thursday, 17 September 2020

Cullinan mine yields blue diamonds

The high quality stones range in size from 9.6 carats to 25.8 carats.South Africa’s Petra Diamonds (LON:PDL), which put itself up for sale in June, announced it has found five high-quality blue diamonds. Petra, which has been hit by a triple whammy of weak market conditions, power emergencies and covid-19, found the Type IIb blue diamonds at its flagship Cullinan mine.

Wednesday, 16 September 2020

High Flower Jewels

Oscar Heyman

Van Cleef & Arpels







Van Cleef & Arpels

Tuesday, 15 September 2020

Gems of the Smithsonian

The Bismarck Sapphire Necklace is a sapphire necklace designed by Cartier in 1935.

It is named after Countess Mona von Bismarck, who donated the piece to the Smithsonian in 1967. The sapphire itself was purchased by the Countess in Sri Lanka in 1926. The necklace consists of a single chain of platinum links connected by pairs of round brilliant cut diamonds. The 98.6 carat table cut Bismarck Sapphire is mounted in a pendant at the front of the necklace, surrounded by baguette-cut diamonds.

The Dom Pedro Aquamarine
The Carmen Lúcia Ruby is a 23.1-carat Burmese ruby set in a platinum ring with diamonds. It was donated by Peter Buck in memory of his wife Carmen Lúcia. The stone was mined from the Mogok region of Burma in the 1930s.

The Blue Heart Diamond was found at the Premier Mine, South Africa in 1908. This 30.62 carat heart-shaped, brilliant cut blue diamond was faceted in 1910 from a 100.5 carat piece of rough.
The DeYoung Red Diamond is one of the largest known natural fancy dark red diamonds. It is a modified round brilliant cut VS-2 diamond of 5.03 carats. The diamond was acquired by S. Sydney DeYoung, a Boston jeweler, as part of a collection of estate jewelry and identified, incorrectly, as a garnet. It was gifted to the National Gem Collection in 1987.
Pink pear shape diamond weighing 2.90 carats.
The Hooker Emerald is 75.47 carats. It was once the property of Abdul Hamid II, Sultan of the Ottoman Empire (1876-1909) who wore it in his belt buckle. Tiffany & Co. purchased the emerald at auction in 1911.

The stone originated from Colombia and was probably shipped to Europe by Spanish conquistadores in the 16th or 17th century. Mrs. Janet Annenberg Hooker donated it to the Smithsonian 1977.
The 58.19-carat Maharani Cat’s Eye from Sri Lanka. The optical phenomenon of chatoyancy can be displayed by many gemstones, but the most popular and highly prized is that of the mineral chrysoberyl.

The “eye” that the stone displays when it is cut cabochon is caused by the reflection of light off numerous parallel inclusions of fine, needle-like crystals, commonly of the mineral rutile.

Hope Diamond

Heart-shaped brooch has a 96-carat amethyst surrounded by diamonds.

The Hall Sapphire Necklace, designed by Harry Winston, Inc., features 36 cushion-cut sapphires from Sri Lanka, totaling 195 carats, set in platinum accented by 435 pear-shaped and round brilliant-cut diamonds, totaling 83.75 carats.

These two large, pear-shaped diamonds weigh 14.25 and 20.34 carats respectively are set in earrings that belonged to Marie Antoinette, the Queen of France who was guillotined in 1793 during the French Revolution.
The Petersen Tanzanite Brooch. Pair of matched tanzanite gems about 30 carats. The floral platinum brooch, designed by Harry Winston in 1991, has 24 carats of diamonds. The tanzanite “flowers” can be detached and worn as earrings. The Petersen Tanzanite Brooch was gifted to the National Gem Collection in 2002.

The Sherman Diamond is one of five pendants from a diamond necklace. The necklace was a gift from the khedive of Egypt to Civil War General William Sherman for his daughter’s wedding in 1874. The necklace was divided among his three daughters. The pendant has an 8.52-carat pear shaped diamond surrounded by 17 round diamonds.

Saturday, 12 September 2020

Madeira Citrine

Citrine is the most popular gemstone in the yellow to orange color range, and one of the most affordable of the harder gems. A variety of crystalline quartz, citrine has excellent transparency and is often found in large sizes, with gems over 20 carats not uncommon.

Though there is a lot of citrine in the market, natural untreated citrine is rare, especially in the more saturated colors, since much of the low-cost citrine sold is treated or synthetic.
Most natural citrine is a pale yellow, the color derives from traces of iron. Many commercial grade citrine in the market have been produced by heat-treating weakly colored amethyst, which will turn yellow at relatively low temperatures.

The most valuable citrines are the natural gems in the saturated colors, known in the trade as Madeira Citrine.

The name derives from a fortified Portuguese wine made in the Madeira Islands.
High quality citrine tends to be very clean, with no eye visible inclusions.

Transparency is excellent, and the material takes a very good polish with a vitreous luster.
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Friday, 11 September 2020

102 carat diamond to be sold without reserve

A flawless 102-carat oval diamond will head to auction on October 5 in Hong Kong at Sotheby's. The egg-shaped stone of 102.39 carats, D colour, Type IIA will be sold without reserve. The gem was cut from a 271-carat rough stone discovered in Ontario's Victor Mine, where production ceased last year.

Only seven other white diamonds of more than 100 carats have appeared at auction. Bidding starts at $1HKD or $.13. In November 2017, the largest diamond ever at auction, 163.41 carats, sold in Geneva for more than $33.8m.

Burma Ruby

Fine ruby is the rarest and most valuable of all colored gemstones. Burma is the traditional source for fine ruby, with new material coming from Madagascar, Tanzania and Mozambique. Treatment is common.

Heat treatment has been used for centuries. It is used to improve the clarity and colour of rubies. The ruby is placed in a crucible and heated to around 1800 degrees.

In 2004, a gem lab in Chanthaburi, Thailand developed a technique to improve the appearance of rubies. Previously undesirable gems could be repaired using heat treatment with lead glass.

The refractive index of corundum and lead glass are similar, allowing light to travel through the stone and improving color and clarity. Fracture-filled rubies sell at a fraction of the cost of untreated rubies of similar color.

Wednesday, 9 September 2020

Green Diamonds

The 5.03 carat Fancy Vivid Green 'Aurora Green' made $16.8m or $3.3m per carat in 2016.
Green diamonds are among the rarest of all fancy colors. The green color is caused by exposure to radiation or radioactivity and is extremely unique.

Natural radiation creates an external skin or surface of green color. It is uncommon for the green color to reach deep within a diamond.
Lab graders assess the natural color of green diamonds by this skin. Irradiated green diamonds are often found in the marketplace, so determining natural color for value is key. Labs may be unable to conclusively determine the natural origin of green diamonds because the cause is radiation.
Green is the color between blue and yellow, so common secondary colors in green diamonds include bluish green and yellowish green, and if the color is desaturated, grayish green or brownish green.

1.56 carat, Fancy Vivid Green Diamond
Natural green diamonds are second to red diamonds as the world's rarest fancy color. True greens devoid of secondary hue are the most valuable among natural green diamonds.

The green diamond has a very strong emotional correspondence with safety as it is the most restful color for the human eye. Green suggests both stability and endurance. Aqua green is associated with emotional healing and protection while Olive green is the traditional color of peace.
The Dresden Green is a 40.70 carat, pear shaped stone with a VS1 clarity grade. It was reported as one of the largest and finest natural green diamonds ever discovered.
The Ocean Dream The diamond is a 5.51-carat, fancy deep blue-green, shield-shaped diamond.

It is the only natural diamond known with this color combination.
The Chopard Chameleon, is a 31.31ct Oval-cut diamond which appears green in bright light but looks yellow in darkness. This stone was one of the first reported by the GIA as a chameleon in the late 1950s.

Cushion-shaped fancy intense green diamond weighing 6.13 carats, within a brilliant-cut pink diamond surround, extending to the half-hoop, mounted in 18k rose gold.

A square-shaped fancy green diamond weighing 10.36 carats, set in a ring within a pear-shaped and round cut pink diamond surround.

3.15 carat, Fancy Intense Yellowish Green diamond. VS1.
Fancy vivid green diamond weighing 2.52 carats. It made $ 3,106,500 CHF at Sotheby's in 2009.