Cullinan IX is a 4.39-carat pear-shaped diamond, the ninth and smallest of the nine principal polished stones cut from the Cullinan rough in 1908. Although modest in size relative to its celebrated siblings — the Cullinan I weighs 530.20 carats and the Cullinan II 317.40 carats — Cullinan IX carries the full weight of the most extraordinary provenance in the history of gem diamonds. It is a Type IIa stone, a classification denoting an absence of measurable nitrogen impurities and, consequently, exceptional optical purity and colourlessness. The diamond is mounted in a platinum ring with a plain band and forms part of the British Royal Collection, having been presented to Queen Mary in 1910. Its diminutive scale among the Cullinan group has never diminished its historical significance: every fragment of the Cullinan rough is, by definition, a fragment of the largest gem-quality diamond ever recovered from the earth.

The Cullinan Rough: Origin and Discovery

The stone from which Cullinan IX was cut was found on 26 January 1905 at the Premier Mine (now the Cullinan Mine) in the Gauteng province of what was then the Transvaal Colony, South Africa. The rough weighed 3,106.75 carats — approximately 621 grams — and measured roughly 10.1 × 6.35 × 5.9 centimetres. It was named after Sir Thomas Cullinan, the chairman of the Premier Diamond Mining Company. The crystal was of exceptional transparency and belonged to the rare Type IIa category, meaning its nitrogen content was below the threshold detectable by standard infrared spectroscopy, a characteristic shared by only a small percentage of gem diamonds worldwide and associated with the finest colourless stones.

The Transvaal government purchased the rough in 1907 for £150,000 and presented it to King Edward VII as a token of loyalty from the recently self-governing colony. The gift carried considerable political symbolism in the aftermath of the Second Boer War. Edward VII entrusted the stone to the Amsterdam firm of Joseph Asscher & Co., then among the most technically accomplished diamond-cutting houses in the world, for cleaving and polishing.

Cleaving and Cutting: Joseph Asscher & Co.

The task of dividing the Cullinan rough fell to Joseph Asscher himself, working alongside his brother Abraham and a team of experienced craftsmen. The operation required months of preparatory study. A groove was first cut into the stone along a natural plane of cleavage, and on 10 February 1908 Asscher struck the first blow with a specially made steel blade. The rough divided cleanly — though not without considerable anxiety, given the irreversibility of the act and the stone's immense value. Subsequent cleaving and sawing operations produced nine principal stones, designated Cullinan I through Cullinan IX, as well as ninety-six smaller brilliants and a quantity of unpolished fragments.

The nine principal stones vary dramatically in size and shape, reflecting both the internal structure of the original crystal and the cutters' decisions about how best to maximise yield and quality from each section. Cullinan IX, the smallest of the group, was fashioned as a pear shape — a cut well suited to elongated or irregular crystal sections and one that displays the stone's exceptional transparency to full advantage. The cutting of all nine principal stones was completed in 1908, a remarkable achievement given the scale and complexity of the project.

Gemmological Character

As a Type IIa diamond, Cullinan IX belongs to a category that accounts for roughly one to two per cent of all gem diamonds. Type IIa stones contain no detectable nitrogen aggregates in their crystal lattice, which eliminates the slight yellow or brown tint that nitrogen imparts to the more common Type Ia diamonds. The result is a stone of the highest colourlessness, transmitting light across a broader ultraviolet-to-infrared spectrum than nitrogen-bearing diamonds. Many of the most celebrated colourless diamonds in history — including the Koh-i-Noor, the Millennium Star, and the other principal Cullinan stones — are Type IIa.

At 4.39 carats, Cullinan IX is a stone of modest commercial dimensions by contemporary auction standards, but its clarity is described as exceptional, consistent with the overall character of the Cullinan rough. The pear shape, with its single point and rounded shoulder, demands precise symmetry and careful attention to the girdle outline; any deviation from a smooth, balanced curve is immediately apparent to the eye. The craftsmanship of Joseph Asscher & Co. ensured that the finished stone met the highest standards of the period.

Presentation to Queen Mary and Royal Provenance

Following the cutting, the principal Cullinan stones were distributed between the British Crown and the South African government, which retained some of the smaller gems. Cullinan IX was among the stones that entered the British Royal Collection. In 1910 it was presented to Queen Mary, consort of King George V, who wore it set in a platinum ring — the setting it retains to this day. Queen Mary was a passionate and knowledgeable collector of jewels, and the Cullinan stones formed a centrepiece of her collection. The plain platinum band of the Cullinan IX ring reflects the aesthetic of the Edwardian and early Georgian periods, when platinum had recently come into widespread use in fine jewellery and was prized for its strength, its white colour, and its ability to display diamonds without the warm reflection of gold.

The ring passed, along with the broader Royal Collection, through the twentieth century and remains in the possession of the British Crown. Unlike Cullinan I and Cullinan II, which are set into the Sovereign's Sceptre with Cross and the Imperial State Crown respectively and are therefore among the most publicly visible jewels in the world, Cullinan IX is a personal jewel rather than a piece of regalia. It has been worn by members of the Royal Family on private and semi-public occasions, though it does not appear in the formal ceremonial rotation of the Crown Jewels held at the Tower of London.

The Nine Principal Cullinan Stones: Context

To appreciate Cullinan IX fully, it is useful to situate it within the sequence of the nine principal stones:

• Cullinan I (530.20 carats, pear shape) — set in the Sovereign's Sceptre with Cross; the largest polished white diamond in the world.
• Cullinan II (317.40 carats, cushion brilliant) — set in the Imperial State Crown.
• Cullinan III (94.40 carats, pear shape) — worn by Queen Mary as a pendant; now part of a brooch.
• Cullinan IV (63.60 carats, square cushion) — also part of Queen Mary's brooch, worn beneath Cullinan III.
• Cullinan V (18.80 carats, heart shape) — set in a brooch.
• Cullinan VI (11.50 carats, marquise) — set in a necklace.
• Cullinan VII (8.80 carats, marquise) — pendant to a Delhi Durbar brooch.
• Cullinan VIII (6.80 carats, oblong brilliant) — set in a brooch with Cullinan VI.
• Cullinan IX (4.39 carats, pear shape) — set in a platinum ring.

The progression from Cullinan I to Cullinan IX is not merely one of diminishing size but of varied form: the cutters selected different shapes for each section of the rough, guided by the internal grain of the crystal and the goal of producing stones of the highest possible quality from each portion. That the ninth stone, at 4.39 carats, is itself a flawless Type IIa diamond speaks to the extraordinary quality distributed throughout the original rough.

The Premier Mine and the Cullinan Legacy

The Premier Mine, renamed the Cullinan Mine in 2003 in honour of the famous stone, continues to produce exceptional diamonds. It has yielded a disproportionate number of large, high-quality Type IIa diamonds relative to other kimberlite pipes, a characteristic attributed to the particular geological conditions of its formation. Among later notable finds from the same mine are the Golden Jubilee Diamond (545.67 carats rough, 545.65 carats polished — the largest faceted diamond in the world by weight) and the Premier Rose. The mine thus occupies a singular position in the history of diamond geology, and the Cullinan rough remains its defining achievement.

The legacy of the Cullinan cutting also shaped the reputation of Joseph Asscher & Co., which subsequently developed the Asscher cut — a square step cut with cropped corners and a distinctive optical pattern — that bears the family name to this day. The firm, now operating as the Royal Asscher Diamond Company following a royal warrant granted by Queen Juliana of the Netherlands in 1980, continues to trade on the prestige of the 1908 commission.

Significance and Assessment

Cullinan IX occupies an unusual position in the canon of famous diamonds. It is not a stone that commands attention through sheer size, nor does it possess the coloured-diamond rarity of a Fancy Vivid blue or pink. Its significance is entirely a function of provenance and pedigree: it is one of nine principal stones cut from the largest gem-quality diamond ever found, fashioned by one of the most accomplished cutting houses in history, and presented to a queen consort of the United Kingdom. In the market for important jewels, provenance of this calibre is irreplaceable. No sum of money can manufacture a connection to the Cullinan rough, to Joseph Asscher, or to Queen Mary's collection.

For the gemmologist, Cullinan IX is a reminder that the significance of a stone is not always proportional to its weight. The Type IIa classification, the pear-shape cutting of exceptional symmetry, and the platinum ring setting of the Edwardian period each contribute to a jewel that is, in its modest way, as historically resonant as the great stones that precede it in the numbered sequence. It is the final chapter of the Cullinan story — the smallest piece of the largest puzzle — and that position carries its own quiet distinction.

Further Reading

• GIA — The Cullinan Diamond
• GIA Gems & Gemology — Type IIa Diamonds