Lot 176. Impressive 6.26-Carat Natural Unheated Brazilian Alexandrite and Diamond Ring. Estimate：HK$ 1,100,000 – 1,500,000／US$ 140,000 – 192,000. Courtesy Tiancheng International.

Centring on a heart-shaped alexandrite weighing 6.26 carats, surrounded by brilliant-cut diamonds extending to the shoulders, mounted in platinum. Ring size: 6

Accompanied by Gübelin report numbered 15040008, dated 8 April 2015, stating that the 6.26 carat alexandrite is natural, Violetish-Green colour in daylight and Purple colour in incandescent light, of Brazilian origin, with no indications of heating; with comments, stating that 'This gemstone displays a strong colour-change'.

Alexandrite

Alexandrite is a colour-changing gemstone from the chrysoberyl family. It is believed that Alexandrite is named after Russian tsar Alexander II as the deposits were discovered in the Ural Mountains on the day he was born. Alexandrite is a gemstone rich in optical effects. Seen in daylight, it will exhibit colour ranging from green to bluish green. Under an incandescent light source such as a candle flame, it will appear brownish red to purplish red. The marvelous changes of colour were looked upon as miracles in ancient times.

A modern scientific explanation attributes the pleochroism of Alexandrite to its selective absorption of light. As the wavelength of green colour is stronger in daylight, the gemstone will display emerald green hues during the day. At night when the wavelength of red colour is stronger, the stone will appear reddish. Alexandrite stones with a more pronounced colour change will fetch higher prices. Nowadays, the Russian mines have been depleted, making Alexandrite extremely scarce. Another source of stunning Alexandrite that shows beautiful colour change is Brazil, but the supply is low. Fine-colour Alexandrite of over 5 carats is exceptionally rare today. 

On offered this season is a 6.26-carat natural unheated Brazilian Alexandrite which had been kept by the collector for over 25 years. Certified by the gem laboratory Gübelin to possess “strong colour change”, the gemstone is distinguished by its excellent clarity and alluring radiance, displaying “Violetish-Green colour in daylight and Purple colour in incandescent light”.

Tiancheng International. HONG KONG SPRING AUCTION, Jewellery and Jadeite. 12 Jun · 1 pm