What Is the Largest Uncut Diamond Known Today
The Cullinan Diamond, discovered in 1905 near Pretoria, South Africa, remains the largest rough diamond ever found and the definitive answer to the question of the biggest uncut diamond in the world. Weighing 3,106.75 carats (621.35 grams) in the rough, it was presented to the British colonial administration and later cut into several polished stones, including the Cullinan I and Cullinan II set in the Crown Jewels. While many large rough diamonds have surfaced since, none have surpassed the Cullinan’s recorded mass. This overview explains its discovery, mineral characteristics, historical evaluation, and enduring legacy in gemology.
Primary Characteristics and Verified Specifications
Understanding the Cullinan requires examining its measurable attributes, geological classification, and how it compares to other notable rough stones. Key specifications are summarized below.
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Name | Cullinan Diamond | Historical records and museum documentation |
| Weight | 3,106.75 carats (621.35 grams) | Gemological Institute of America, South African archives |
| Color | White to colorless, with possible gray | Contemporary assay reports |
| Clarity | Type IIa, with minor inclusions | Laboratory grading summaries |
| Crystal Form | Octahedral | Mineralogical analysis |
| Cutting Outcome | Produced 9 major stones, including Cullinan I and II | Historical cutting records |
| Current Location of Main Stones | Crown Jewels, United Kingdom | Royal Collection and Tower of London |
Definition and Classification
In gemology, a Type IIa diamond is chemically pure and structurally perfect, making them rare and valuable. The Cullinan’s octahedral habit is consistent with formation under high pressure and temperature in the Earth’s mantle, then transported rapidly via kimberlitic volcanism. Its clarity, while not flawless, remains strong by uncut standards, with inclusions typical of natural crystals that were identifiable under microscopic examination after cutting.
Comparison With Other Notable Rough Diamonds
- Cullinan (1905, 3,106.75 carats) – South Africa; largest recorded uncut diamond.
- Lesedi La Rona (2015, 1,109 carats) – Botswana; second largest gem-quality rough.
- Excelsior (1893, 995 carats) – South Africa; held record prior to Cullinan.
- Sergio (1895, ~3,167 carats) – Brazil; heavier but lower gem quality, mostly industrial use.
While Sergio is technically heavier, the Cullinan is universally recognized as the largest gem-quality uncut diamond and the most significant in jewelry history.
Discovery and Recovery Details
The Cullinan was found on 26 January 1905 by Frederick Wells, surface manager at the Premier No. 2 mine owned by the Premier Diamond Mining Company in Cullinan, Transvaal Colony. The stone was embedded in the face of a steep wall, attached to a matrix that initially disguised its true scale. It was extracted using controlled blasting and careful hand tools, then transported to the surface under discreet conditions to prevent theft. The rough crystal measured approximately 10.1 centimeters (4 inches) in length and weighed 3,106.75 carats. Its discovery immediately attracted international attention, prompting heightened security and diplomatic protocols during its transfer and evaluation.
Immediate Evaluation and Ownership
After recovery, the diamond was sent to the Netherlands for assessment by experienced cleavers and cutters, as South Africa lacked established facilities at the time. The assessment concluded that the stone’s exceptional size and clarity justified a cautious, multi-phase cutting plan. Ownership was eventually negotiated: the Premier Mine sold the Cullinan to the Transvaal Colony government, which presented it as a birthday gift to King Edward VII. This sequence reinforced the diamond’s role as both a geological specimen and a national diplomatic instrument.
Cutting Process and Resulting Major Stones
The cutting of the Cullinan is among the most studied episodes in gem history. Joseph Asscher & Co. of Amsterdam, renowned for their precision, undertook the work. The process began with a week-long study of the crystal’s internal structure, followed by a carefully planned split along a natural cleavage plane. The initial division produced two major sections, from which nine principal polished stones were eventually fashioned. Notably, Cullinan I (the Great Star of Africa) and Cullinan II (the Lesser Star of Africa) are set in the Imperial State Crown and the Sovereign’s Scepter with Cross, respectively. These stones remain part of the UK Crown Jewels and are among the most recognized gems in the world.
Resulting Diamonds from the Cullinan
| Stone | Weight (carats) | Cut | Current Use |
|---|---|---|---|
| Cullinan I | 530.20 | Round brilliant | Set in the Imperial State Crown |
| Cullinan II | 317.40 | Marquise | Set in the Sovereign’s Scepter |
| Cullinan III | 94.40 | Cushion brilliant | Part of the Crown Jewels set pieces |
| Cullinan IV | 63.60 | Baguette | Set in the Crown Jewels |
| Cullinan V | 18.80 | Pear | Often paired with Cullinan III |
| Cullinan VI–IX | Various smaller stones | Brilliant cuts | Used in parures and regalia |
Market, Value, and Ethical Considerations
Because the Cullinan was a gift to the British Crown rather than a market sale, its price was not publicly established. Analysts have estimated that if sold as a polished gem at modern luxury valuations, the yield could reach hundreds of millions of dollars, factoring in color, clarity, and historical significance. These remain hypothetical figures, as the stone has never been traded and is not for sale. Ethical questions around colonial-era acquisitions persist, focusing on transparency, stewardship, and the equitable recognition of origin regions. Responsible custodianship, conservation science, and inclusive interpretation are widely regarded as appropriate approaches to managing such culturally significant objects.
Scientific Studies and Preservation
Advanced spectroscopic and imaging techniques have been employed to study the Cullinan’s internal features, growth zoning, and trace element profile. These studies have clarified its geological provenance and provided benchmarks for understanding super-large diamond formation. Today, the principal stones are stored in secure, low-vibration environments within the Crown Jewels collection, with periodic condition assessments ensuring long-term stability. Public exhibitions are scheduled judiciously to balance access with conservation, and viewing protocols prioritize preservation and security.
Enduring Legacy and Public Interest
The Cullinan continues to shape popular and scholarly understanding of diamond genesis, cutting craftsmanship, and cultural symbolism. Its presence in regalia connects viewers to early 20th-century mining history and geopolitical contexts, while ongoing research reinforces its status as an object of enduring scientific and aesthetic interest. For gemologists, historians, and enthusiasts, the Cullinan represents the pinnacle of uncut diamond records and remains a foundational reference point in the field. This profile is intended as a durable, verifiable resource for ongoing inquiry into the world’s largest uncut diamond and its multifaceted significance.