The Jonker V diamond, one of 13 magnificent diamonds cleaved from the famous 726-carat Jonker rough more than 80 years ago, will go under the hammer on May 30 at Christie's Hong Kong. The 25.27-carat emerald-cut gem is expected to fetch upwards of $3.6 million.

On January 17, 1934, a rough diamond the size of a hen's egg was pulled from a bucket of gravel at the Elandsfontein claim, 4.8 kilometers south of the Premier Mine in South Africa. The massive 726-carat rough diamond with a frosty ice-white color would take on the surname of the 62-year-old digger who owned the claim. His name was Jacob Jonker.

At the time, the Jonker was the fourth-largest gem-quality rough diamond ever unearthed. Diamond experts speculated whether the 63.5mm-by-31.75mm Jonker and the 3,106-carat Cullinan Diamond had once been conjoined, as their respective cleaved faces seemed to match up perfectly. The Cullinan Diamond had been discovered at the nearby Premier Mine 19 years earlier.

The Jonker rough was acquired by De Beers chairman Sir Ernest Oppenheimer and subsequently caught the attention of diamond dealer Harry Winston, who purchased the stone in 1935 for £75,000, the equivalent of £9 million ($11 million) today. The Jonker rough diamond earned celebrity status when it was displayed during the Silver Jubilee Celebrations of the Coronation of King George V and Queen Mary in May of that same year.

The next year, Winston contracted Lazare Kaplan to cut 13 finished gems from the original rough. The Jonker finished diamonds were each named with a Roman numeral, in size order. The largest was the Jonker I at 142.90 carats and the smallest was the Jonker XIII at 3.53 carats. According to a May 1954 article in The New Yorker, Kaplan was paid $30,000 for his work.

Before cutting, the Jonker V rough weighed 54.19 carats, more than twice its finished weight. The beautiful emerald-cut gem boasts a D-color and a VVS2 clarity grading. Christie's posted a pre-sale estimate of $2.2 million to $3.6 million, but some industry experts are expecting the Jonker V to sell for much more.

Credit: Images courtesy of Christie's.