The stone

The Incomparable Diamond is a shield-cut deep brownish-yellow (fancy intense yellow) diamond weighing four hundred and seven and forty-eight hundredths carats, cut from a rough crystal of eight hundred and ninety carats discovered in the early 1980s in the Mbuji-Mayi region of the Democratic Republic of the Congo. After cutting, it is the third-largest polished diamond in the world by carat weight, behind the Cullinan I in the British Sovereign's Sceptre and the Golden Jubilee in the Royal Thai Treasury.

The discovery story

The discovery of the rough is one of the more unusual provenance stories in diamond history. According to the principal published accounts, the rough was found in approximately 1984 by a young girl playing in a heap of rubble outside her uncle's house in Mbuji-Mayi. The rubble had been brought from the diamond-mining area, and the girl found the rough crystal among the discarded material. The crystal was sold to a local Lebanese trader, Kazi Senoussi, who recognised its potential significance and resold it to a dealer in Antwerp.

The provenance from a child's discovery in mining-area rubble through an artisanal trader to the international market is characteristic of the Mbuji-Mayi region's small-scale mining sector and contrasts sharply with the carefully controlled discovery of stones from major industrial mines such as the Premier in South Africa.

The cutting

The eight hundred and ninety carat rough was cut by Marvin Samuels of Premier Gem Corporation in New York between 1984 and 1988, a four-year process that involved extensive study, model-making and incremental shaping. The result was a single principal stone of four hundred and seven and forty-eight hundredths carats in a triangular shield brilliant cut, plus fourteen smaller stones cut from the surrounding material. The shield form, an unusual choice, was selected to maximise yield from the irregular rough shape.

The colour is deep brownish-yellow, designated by GIA as fancy intense yellow with brown overtones. The clarity is internally flawless. The cutting style maximises light return through a relatively shallow shield form with extensive faceting on both crown and pavilion.

The auction history

The Incomparable was unveiled in 1988 and was offered at Christie's New York that year with an estimate of twenty million US dollars. It did not sell at the auction. The stone subsequently passed through several private treaty arrangements without changing hands at the asking price.

In 2002 it was again offered, this time on eBay, in what was the highest-valued single item ever offered on the platform at that time. It did not sell. In 2013 the stone was reset by Mouawad as the centre stone in a necklace called L'Incomparable, with ninety smaller diamonds in the surround, and was reportedly listed at fifty-five million US dollars in private treaty.

The political context

The Incomparable's emergence from the Congolese mining sector during the closing years of the Mobutu Sese Seko regime, and the broader Congolese diamond trade's role in funding conflict during the subsequent civil wars from 1996 onward, places the stone in a politically charged context. The Mbuji-Mayi region, while not the principal locus of conflict-diamond production (which was concentrated in the eastern Congo, in Sierra Leone, Liberia and Angola), was nonetheless connected to the broader conflict-diamond crisis that emerged in the late 1990s and led to the establishment of the Kimberley Process Certification Scheme in 2003.

The Incomparable predates the Kimberley Process by approximately fifteen years and was sold internationally before the conflict-diamond awareness emerged. The stone is not therefore subject to the Kimberley Process certification, but its provenance from the Congolese mining sector during a period of political instability is part of its broader historical context.

The market difficulty

The Incomparable's repeated failure to sell at its asking price illustrates a recurring pattern in the very-large-stone market. Stones above three hundred carats have a thin buyer pool, and the asking prices for such stones often exceed what the available buyers will pay. The buyer pool consists principally of central banks, sovereign wealth funds, museums, and a small number of ultra-high-net-worth individuals; commercial jewellers do not generally buy at this scale because the resale market is similarly thin.

The Cullinan diamonds, by contrast, were absorbed into the British Crown Jewels through a sovereign gift, removing them from the commercial market entirely. The Golden Jubilee was acquired by the Thai monarchy through a gift coordinated by Henry Ho. The Incomparable's situation, in which a privately held very-large stone has not found an institutional or sovereign buyer at the asking price, is the more common outcome for such stones.

Place in the canon

For the working trade, the Incomparable is significant for several reasons. It demonstrates the cutting capacity of contemporary New York lapidary practice in the late twentieth century. It illustrates the distinct yield characteristics of unusually shaped rough crystals. It shows the market dynamics for very-large stones, in which the asking price and the achievable price can diverge substantially. And it stands as a reminder that the very largest stones generally find institutional rather than private commercial buyers.