The world's largest uncut diamond is the Cullinan Diamond, a 3,106-carat gem discovered in 1905 at the Premier No. 2 mine near Cullinan, South Africa. It was presented to Britain's King Edward VII and subsequently cut into several polished stones, including the Cullinan I and Cullinan II set in the Imperial State Crown and other Crown Jewels. This overview explains its remarkable physical characteristics, mining origin, historical ownership, and realized value, based on authoritative mineralogical and historical records rather than speculation. The following sections detail verified attributes, subsequent processing, and its enduring status as the largest gem-quality rough diamond ever found.
The Cullinan Diamond: Core Facts
The Cullinan Diamond is universally recognized as the largest gem-quality rough diamond ever recovered. Weighing 3,106 carats (621.2 grams), it was discovered on 26 January 1906 at the Premier Diamond Mining Company in Cullinan, Transvaal Colony. Its exceptional clarity and lack of significant inclusions made it suitable for precision cleaving and brilliancy cutting rather than polished carving as a single stone. After careful assessment by experts, it was entrusted to renowned diamond cutter Joseph Asscher in Amsterdam.
Physical Characteristics and Classification
Before cutting, the Cullinan measured approximately 10.1 centimeters (4 inches) in length, with a width of 6.35 centimeters (2.5 inches) and a height of 5.08 centimeters (2 inches). Mineralogically, it is classified as a type IIa diamond, indicating minimal nitrogen impurities and exceptional optical transparency. Its toughness and cleavage planes enabled precise segmentation, transforming a singular mass into multiple polished components used in significant ceremonial jewels.
Key Specifications at a Glance
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Name | Cullinan Diamond | Historical records |
| Weight | 3,106 carats (621.2 g) | Mine reports and gemological assays |
| Discovery Date | 26 January 1905 (reported 1906) | Mine documentation |
| Location | Premier No. 2 mine, Cullinan, South Africa | Geological surveys |
| Post-cutting notable polished stones | Cullinan I (530 ct) and Cullinan II (317 ct) | Gemological records |
| Type | Type IIa, high clarity | Laboratory classification |
Discovery and Initial Assessment
The diamond was discovered by Frederick Wells, a surface manager at the Premier Mine, in January 1905. Initially mistaken for a piece of glass due to its size and crystalline perfection, it was later authenticated as a rare large gemstone. The mine's owners notified British businessman Thomas Cullinan, who subsequently sold it to the Transvaal government. It was then presented as a birthday gift to King Edward VII in 1907 by the Crown Colony of the Transvaal, intended to strengthen ties between Britain and the Transvaal after the Second Boer War.
Cutting and Division
Joseph Asscher and Company in Amsterdam evaluated the stone for months before attempting to cleave it. The first critical split revealed a weaker internal structure than anticipated, leading to a carefully planned sequence of cuts. Ultimately, the Cullinan was divided into nine major stones and around 100 smaller brilliants. The two largest polished pieces—Cullinan I and Cullinan II—were selected for integration into British Crown Jewels, while other fragments were distributed among private and institutional collections. This process exemplified the precision required to maximize light performance from an unmatched rough mass.
Current Locations and Ownership
Following integration into the Crown Jewels, Cullinan I (the Great Star of Africa) is set in the Sovereign’s Scepter, and Cullinan II is set in the Imperial State Crown, both on public display at the Tower of London as part of the Crown Jewels collection. Smaller brilliants from the original rough are held privately or in museum collections. Ownership of the major polished stones is vested in the British monarchy and managed within the Crown Jewels inventory, ensuring their preservation and controlled public access.
Value and Market Context
As an uncut specimen, the Cullinan Diamond has no single market price comparable to polished gems. Its value is often estimated in historical and educational contexts, with pre-cutting assessments placing its worth at several million pounds in early 20th-century terms. Subsequent sales of related polished stones, such as Cullinan I and II, occurred at auction decades after integration, but prices are not directly indicative of the original rough value. Insurance valuations, if disclosed, would reflect replacement costs for comparable high-clarity Type IIa material rather than a tradable market price.
Enduring Significance
The Cullinan Diamond remains the benchmark for size and quality in gemology. Its careful study has informed modern understanding of super-large diamond formation and clarity preservation. Museums, gemological institutes, and historical archives reference it as a definitive example of nature's capacity to produce rare materials at scales that challenge cutting and display techniques. As the largest uncut diamond recovered and subsequently preserved in prestigious faceted form, it continues to anchor conversations about geological rarity, craftsmanship, and heritage stewardship.