An exceptional fancy coloured diamond and diamond ring, by Kwiat. Photo Bonhams.

The radiant-cut fancy pink diamond, weighing 5.13 carats, within a delicate border of brilliant-cut diamonds, the shoulders of crossover design set with similarly cut diamonds, signed Kwiat, ring size 6. Estimate HK$ 11.2 million - 13.2 million (€1 million - 1.2 million)

Accompanied by a GIA report stating that the 5.13 carat diamond is natural Fancy Pink colour and VS2 clarity. Report number 1132418669, dated 21 March 2013.

Pink diamonds are extremely rare. Approximately 1 in 10,000 carats of mined diamonds are gem quality fancy coloured diamonds. Of this small amount 0.01% are fancy pink diamonds and only a handful of these are over 2 carats.

A coloured diamond's rareness is further multiplied when there is no secondary hue and the body colour is of high enough saturation to be deemed fancy colour. Fancy coloured diamonds are graded in 12 colour categories with over 90 secondary hues and 9 grades of colour saturation, which results in over 230 colour combinations.

The majority of pink diamonds have a characteristic secondary hue, such as purplish pink or orangy pink and they can be heavily included; fancy coloured diamonds with clarity grades of VS2 or better are extremely hard to find.

Currently, the famous Argyle mine in North West Australia accounts for 90% of worldwide pink diamond production and the life expectancy of the Argyle mine is anticipated to be up until 2020.

With no major diamond discoveries in the last two decades, good quality, fancy pink diamonds of all sizes are expected to remain highly sought after and increasingly difficult to find.

Sam Kwiat arrived in the United States on a steamship from Europe. In 1907 he opened a diamond jewelry store in the heart of New York City's diamond district and quickly earned a reputation as a skilled diamond merchant who was highly regarded for his expertise in cutting exceptional diamonds.

Sam's son, David, joined the family business in 1933. Like his father, David was a talented craftsman who, over time, formed an impressive collection of important diamond jewelry that could be found at the most exclusive shops on New York's Fifth Avenue and around the world.

By the 1960's David had become a renowned diamond merchant. It is documented that in 1965 he purchased a 126-carat rough diamond that yielded the 50-carat "Teardrop of Africa" cut for Harry Winston. This cemented his reputation as one of the finest diamond cutters in the world.

In 2007, in celebration of their 100th anniversary, the Kwiat family opened their flagship boutique in New York City's luxury shopping district on Madison Avenue.

To this day, Sam's grandsons and great-grandchildren continue to operate the business whilst remaining dedicated to the family legacy of integrity, quality, craftsmanship and design.

Bonhams. FINE JEWELLERY & JADEITE. Hong Kong, Admiralty, 21 May 2014 - www.bonhams.com