Allnatt Diamond: A New Chapter

There's an element of mystery to every notable diamond, and the 101.29-carat fancy vivid yellow Allnatt Diamond is no exception.

What we do know is that the Type 1a VS2 gem is to be auctioned by Sotheby's Geneva next Tuesday (14 May) with an estimate of CHF 5.6m to CHF6.5m ($6.16m to $7.15m).

We know it takes its name from the British art enthusiast, soldier, sportsman philanthropist, racehorse owner and property tycoon Major Alfred Ernest Allnatt (1889 to 1969).

We also know that although the stone was originally cut to 102.07 carats and was GIA-graded as fancy intense yellow, it was later repolished down to its current 101.29-carats, which boosted its color to fancy vivid yellow.

But there are some missing pieces from the jigsaw. It's unclear where or when it was recovered, nothing appears to be known of its provenance prior to Allnatt buying it in the early 1950s, and the identity of its current owner is, not surprisingly, also a secret.

The Allnatt diamond was likely - but not definitely - recovered at what was then the Premier Mine, in South Africa, operated by De Beers and famous for its blue diamonds. The mine was subsequently renamed Cullinan and was sold in 2017 to Petra Diamonds.

The old-style shape of the Allnatt Diamond - round-cornered square brilliant-cut - suggests it was manufactured before the use of sawing and that its shape mirrors the outline of the original rough, but we don't have a firm date.

Major Allnatt was the first documented owner, but it's entirely possible there were others before him. We know that in 1952 he took the stone to Cartier to have it mounted as a brooch and that the job was completed and invoiced in September 1953.

He had the Allnatt diamond set as the heart of a flowerhead with five brilliant-cut diamond-set petals, a stem and two leaves enhanced with baguette diamonds.

In May 1996 the brooch was sold at auction by Christie's in Geneva for $3,043,496. Its property designation read 'Property of a Lady'. Allnatt had been dead for almost 30 years so we can only speculate as to its ownership at the time.

It was bought by SIBA Corporation, the diamond company founded by Sam Abram, a De Beers sightholder who was born in Afghanistan, moved to the USA and died in 2019. SIBA had the stone re-cut and re-graded as fancy vivid yellow.

Since then it has made two public appearances, in 2003 and 2005 exhibitions at the Natural History Museum of the Smithsonian Institution in Washington, DC.

At some point it has, reportedly, been "in the hands of an anonymous diamond collector in New York City", but it's not clear who is the current owner. Even less so who the next one will be.

Have a fabulous weekend.