The Williamson Pink Diamond is a 23.6-carat round brilliant-cut pink diamond discovered at the Mwadui mine in Tanganyika (now Tanzania), owned by Canadian geologist John Williamson. Pink diamonds of this size and quality are among the rarest gemstones in the world, and the Williamson stone was exceptional in coming directly from a mine rather than from an existing collection or auction.
The wedding gift
In 1947, Williamson gave the stone as a wedding present to Princess Elizabeth and Prince Philip. It arrived unmounted, and the question of how to set it was left to the princess. She chose a jonquil-flower design, with the diamond as the central bloom. Cartier London was commissioned to execute the piece.
The brooch and its making
The flower form (a jonquil, a variety of narcissus) placed the stone at the heart of a platinum setting: petals of brilliant-cut diamonds, leaves of marquise-cut diamonds, and a stem of baguette-cut diamonds. The design keeps the pink of the diamond as the dominant visual element rather than competing with it. The work was carried out by the English Art Works workshop on the upper floors of 175 New Bond Street. The brooch was completed in time to be worn publicly in the years following the wedding, and it remained a piece Queen Elizabeth II wore on notable occasions throughout her reign. It is now part of the Royal Collection.
Provenance and rarity
What made the Williamson stone unusual was not only its colour and size but the directness of its journey from earth to jeweller. Most major diamonds of the twentieth century passed through dealers, auctions, and multiple hands before reaching a setting. The Williamson diamond arrived at Cartier London with an unusually clean provenance line, which added to its historical interest. The mine at Mwadui continued to produce pink diamonds after 1947, though none have matched the Williamson stone's combination of size and colour saturation.
Sources
- Francesca Cartier Brickell, The Cartiers (Ballantine Books, 2019), ch. 10 (“Cousins in Austerity, 1945–1956”)
- Royal Collection Trust, The Queen's Diamonds (2012)
- “Queen Elizabeth's favourite diamond brooch”, The Daily Telegraph, 22 August 2025
- Wikipedia: Williamson Pink Diamond
