The Mirror of Great Britain was a large diamond owned by James I of England in the early seventeenth century, set into a composite jewel of the same name that incorporated several major stones from the unified English and Scottish royal collections. The jewel and its principal diamond are documented in royal inventories of the early Stuart period but disappeared during the dispersal of the Crown Jewels following the 1649 execution of Charles I.

The jewel

James I commissioned the Mirror of Great Britain in 1604, shortly after his accession to the English throne and the merger of the Scottish and English royal collections. The jewel was designed to symbolise the union of the two crowns, its title evoking both the optical clarity of its principal stone and the political idea of a common reflection in a single regalia. The jewel incorporated the Great Sancy diamond — a separate famous diamond purchased from the Sancy collection — and several other significant stones, set in a goldsmith's composition recorded by the royal goldsmith George Heriot.

The principal central diamond, distinct from the Sancy, was a large table-cut stone selected for its exceptional clarity and the perfectly flat polish of its principal facet, a quality that gave it a mirror-like reflective character much prized in Renaissance and early-Baroque lapidary aesthetics before the development of the brilliant cut and the corresponding emphasis on dispersion and brilliance through pavilion facets.

Documentary record and disappearance

The jewel is documented in several Stuart-period inventories and in correspondence relating to the royal collection. Its disappearance came during the Commonwealth period, when Parliament authorised the sale of the Crown Jewels following the abolition of the monarchy in 1649. Many royal jewels were broken up and the stones sold individually; some were melted for the gold content. The Mirror of Great Britain is thought to have been disassembled in this dispersal, with its component stones — including the central table-cut diamond — sold separately. No record of the principal diamond's subsequent ownership has been confidently established.

Some scholars have proposed that the central stone may have been recut and incorporated into later pieces, but no documented chain of custody supports any such identification. The 1649 dispersal effectively erased the documentary trail of many Stuart jewels, and post-Restoration efforts under Charles II to recover them recovered a fraction at best.

In the historical record

The Mirror of Great Britain is one of several Renaissance and early-modern jewels whose disappearance during major political ruptures has left them as named entries in the historical record without surviving objects to attach the names to. The jewel's importance lies as much in what it represented — the Stuart unification of the crowns — as in its physical form. For the diamond trade and historical-jewellery scholarship, the piece is an instructive case of how jewellery and political symbolism intertwine, and how that symbolism can be physically dissolved by the upheavals of the periods that produced it.

Further reading

• Royal Collection Trust — Crown Jewels and Stuart-period regalia
• British Museum — Stuart and Tudor jewellery
• Victoria and Albert Museum — early modern European jewellery