The Black Prince's Ruby: A Spinel in Disguise

## The Crown's Red Jewel Set prominently in the front of the British Imperial State Crown, directly above the Cullinan II diamond, sits a large, irregularly shaped red gemstone known as the Black Prince's Ruby. At approximately 170 carats (uncut and unpolished — it has never been faceted), it is one of the most historically significant gems in the British Crown Jewels. There is one problem with its name: it is not a ruby. It is a red spinel — a different mineral entirely. This misidentification, which persisted for centuries, is one of the most famous cases of gemological confusion in history. ## Spinel vs. Ruby: The Confusion The confusion between spinel and ruby is understandable. Both stones: - Occur in the same geological environments (metamorphic marble deposits) - Can display identical vivid red colors - Are mined from the same deposits (particularly in Burma, Sri Lanka, and Central Asia) - Were historically found together in gem gravels Before modern mineralogy (developed in the late 18th century), there was no way to distinguish them without sophisticated testing. Both were simply called "ruby" — or, in the case of particularly fine large red spinels, "balas ruby" (a term derived from Badakhshan, a region in modern Afghanistan/Tajikistan that was a major historical source). The key differences between ruby and spinel: | Property | Ruby (Corundum) | Spinel | |----------|----------------|--------| | Chemistry | Al₂O₃ | MgAl₂O₄ | | Crystal system | Trigonal | Cubic | | Hardness | 9 | 8 | | Refractive index | 1.762-1.770 | 1.712-1.736 | | Optic character | Doubly refractive | Singly refractive | ## The Stone's Journey ### Origin The Black Prince's Ruby likely originated in the mines of Badakhshan (in what is now northeastern Afghanistan or Tajikistan), which produced many of history's great spinels. The region's mines have been active for over 1,000 years. ### Abu Sa'id and Don Pedro The stone's documented history begins in 14th-century Spain. According to historical accounts, the spinel was owned by Abu Sa'id, the Moorish Prince of Granada. In 1362, Don Pedro the Cruel, King of Castile, invited Abu Sa'id to his court at Seville, ostensibly for negotiations. Don Pedro had Abu Sa'id murdered and seized his jewels, including the great red stone. ### The Black Prince In 1367, Don Pedro sought military aid from Edward, Prince of Wales — known to history as the Black Prince. Edward, the eldest son of King Edward III of England, led an army into Spain to support Don Pedro's claim to the Castilian throne. After the Battle of Najera (1367), Don Pedro rewarded Edward with the great red stone. Edward brought the stone to England, and it entered the English royal collection. From this point, the stone's history is intertwined with English (later British) monarchs. ### Henry V at Agincourt The most dramatic moment in the stone's history came at the Battle of Agincourt (1415). King Henry V wore a golden helmet crowned with jewels, including the red spinel. During the battle, Henry was struck on the head by the Duke of Alencon's sword — a blow fierce enough to knock off a piece of the crown. The helmet (and the stone) survived the battle, and Henry's victory became legendary. Some accounts state that the stone was damaged during the battle and subsequently repaired — the Black Prince's Ruby has a visible surface irregularity that may date from this incident or from an earlier drilling (the stone has a partially filled drill hole at the top, suggesting it was once worn as a bead or pendant). ### Civil War and Restoration When Oliver Cromwell's Parliament abolished the monarchy and sold the Crown Jewels in 1649, the spinel was valued at four pounds. Its subsequent history during the Interregnum is unclear — it may have been purchased by a sympathizer and preserved, or it may have been among jewels that were recovered rather than sold. At the Restoration of Charles II in 1660, the Crown Jewels were reconstituted, and the Black Prince's Ruby was incorporated into the new State Crown. ### The Imperial State Crown The current Imperial State Crown was made in 1937 for the coronation of George VI. The Black Prince's Ruby is set in the front center cross pattee, directly above the 317.40-carat Cullinan II diamond and below the St. Edward's Sapphire. The stone is set in its original, unfaceted form — a polished but irregular cabochon shape that preserves its medieval character. ## Gemological Analysis Modern gemological testing has confirmed that the Black Prince's Ruby is: - Red spinel (MgAl₂O₄) - Approximately 170 carats (exact weight unknown — the stone has never been removed from its setting for precise measurement) - Uncut and unpolished (retaining its original crystal-derived shape) - Features a partially filled drill hole at the top, plugged with a small ruby cabochon The stone has never been faceted, which is unusual for a gem of its importance. This preservation of the original form may reflect respect for the stone's antiquity, or it may simply reflect the historical reality that faceting technology was not available when the stone entered the English crown. ## The Other Famous Spinels The Black Prince's Ruby is not the only famous spinel mistaken for a ruby: **The Timur Ruby** (352 carats): Also in the British Crown Jewels, inscribed with the names of six Mughal emperors. Confirmed as spinel. **The Samarian Spinel** (500 carats): The largest known polished spinel, in the Iranian Crown Jewels. Originally classified as a ruby. **The Catherine the Great Ruby** (398.72 carats): Set in the Russian Imperial Crown. Confirmed as spinel. These examples demonstrate that the most prized "rubies" of the medieval and early modern periods were frequently spinels — a testament to spinel's beauty and to the limitations of pre-modern gemological knowledge. ## Significance The Black Prince's Ruby represents a remarkable survival. It has passed through the hands of Moorish princes, Castilian kings, English warrior-princes, Tudor and Stuart monarchs, and survived civil war, possible battlefield damage, and 650+ years of history. Its identification as spinel rather than ruby does not diminish its value or significance — if anything, it enhances the stone's story, adding a layer of scientific discovery to its already extraordinary provenance.