The Moussaieff Red — The Largest Known Fancy Red Diamond
The Moussaieff Red — The Largest Known Fancy Red Diamond
A 5.11-carat triangular brilliant in the rarest of all diamond colour grades, formerly the Red Shield
The Moussaieff Red is the largest known fancy red diamond, weighing 5.11 carats in a triangular brilliant cut and graded by the Gemological Institute of America as Fancy Red — the highest possible saturation grade in the red colour family and the rarest of all GIA fancy-colour designations. The stone was acquired by Moussaieff Jewellers Ltd of London from its previous owner the William Goldberg Diamond Corporation, which had cut it in the late 1990s from a thirteen-carat rough discovered earlier in the decade. Before its acquisition by Moussaieff the polished stone was known as the Red Shield Diamond. Its current designation honours the firm of Alisa Moussaieff, the London-based haute joaillerie and high-jewellery house long associated with the trade in important coloured diamonds.
Why red diamonds are exceptional
Pure red is the rarest of all diamond colours. The Gemological Institute of America has graded fewer than thirty diamonds with the unmodified Fancy Red designation in its history, of which the great majority are below one carat in weight. By comparison, fancy yellow, brown, and even blue diamonds occur in commercial quantities; pink diamonds, while rare, are produced regularly from the Argyle mine in Australia (closed in 2020) and a handful of other sources. True reds — without modifying purplish, brownish, or pinkish tones — are statistical outliers in the diamond population.
The cause of red colour in diamond is generally attributed to plastic deformation in the crystal lattice, which produces lattice defects that absorb across most of the visible spectrum and transmit selectively in the red. The same mechanism produces pink diamonds, with red representing the deepest expression of the same colour-causing process. Red diamonds typically come from the same provenance as the most saturated pink diamonds: the Argyle mine in Australia, certain Brazilian deposits, and occasional examples from African mines. The Moussaieff Red was discovered in the Abaetezinho river in Brazil in the mid-1990s by an artisanal miner.
The cut and the cutter
The original rough weighed 13.9 carats. The cutting was undertaken by William Goldberg's firm in New York, with the strategic decision to maximise face-up colour saturation rather than carat weight retention — a calculation that traded the much larger possible size for the higher per-carat value of a more saturated finished stone. The triangular brilliant cut was selected as best suited to concentrate the colour in the face-up view; the cut is occasionally described as a trilliant, though triangular brilliant is the more accurate description. The finished stone weighs 5.11 carats and grades internally flawless in clarity, an additional rarity that contributes to its position at the apex of the red diamond market.
Provenance and ownership
Following the cut, the stone was held by the William Goldberg Diamond Corporation under the Red Shield name. It was sold to Moussaieff Jewellers Ltd of London, which retained it in inventory and exhibited it on multiple occasions, including loans to major museums. The Moussaieff family is one of the oldest dynasties in the international diamond trade, with origins in the Bukharian Jewish community and successive generations active in the trade in important coloured diamonds. The firm has handled multiple historically significant stones over its history, of which the Moussaieff Red is among the most consequential.
The stone has been displayed at the Smithsonian National Museum of Natural History as part of the museum's exhibition of important diamonds, alongside the Hope, the Portuguese, and other famous specimens. Its valuation is rarely cited authoritatively in the public record, but informed estimates from the dealer and auction trade place it well into the tens of millions of dollars, with some commentators suggesting that a public sale would test the upper limit of any auction record for a coloured diamond.
Colour and grading
The GIA fancy-colour grading system places the Moussaieff Red in the highest available position for a red diamond: Fancy Red, with no modifying terms. The next lower grade — Fancy Purplish Red, Fancy Brownish Red, or Fancy Pink — represents a substantial reduction in market value. The unmodified Fancy Red is reserved for stones whose hue, tone, and saturation fall within a tightly defined region of the colour space, and the relative scarcity of stones meeting this standard is the principal driver of the category's value premium.
The clarity grade — internally flawless — is itself remarkable for a strongly coloured diamond. The plastic deformation that produces the red colour often correlates with internal strain features that limit the achievable clarity grade; an internally flawless red of this size is essentially without parallel.
The market for red diamonds
The market for fancy red diamonds is exceptionally thin. The handful of stones in circulation trade in private transactions or in carefully curated auction lots, and the public price record is correspondingly limited. The Hancock Red, a 0.95-carat purplish-red diamond, sold at Christie's in 1987 for over $880,000, equivalent to over $926,000 per carat in 1987 dollars; this remained the per-carat record for a coloured diamond for many years and helped establish the price plateau for the category. The Argyle Pink Diamonds Tender — the annual sale of the finest pink and red diamonds from the Argyle mine, conducted from 1984 until the mine's closure in 2020 — was the principal regular source of red diamonds entering the high-end trade, and the Tender's results consistently set per-carat benchmarks well above all other coloured-diamond categories.
The Moussaieff Red has not been offered at public auction. Its market value is therefore a matter of dealer opinion rather than verified record, but its size, clarity, and colour designation place it without question at the absolute top of the category.
In the trade
Red diamonds occupy a unique position in the high-end coloured diamond trade: scarce enough that an individual important stone can become a generational asset, yet sufficiently established as a category that the market mechanism supports liquidity at the right price. The Moussaieff Red is the most-discussed example of the category, frequently cited in trade press as a benchmark for the upper end of red diamond pricing. For collectors building exposure to coloured diamonds, the Moussaieff Red sets the aspirational ceiling; for the broader market, it serves as the proof of concept that red diamonds can exist at sizes capable of supporting the most ambitious high jewellery designs.