King of Thailand owns “World's Largest Diamond”, a 545.67-carat gem
A brown diamond weighing 545.67 carats and known as the Golden Jubilee sits among Thailand’s most visible royal treasures. The polished stone holds the record for the largest cut and faceted diamond in the world and was presented to King Bhumibol Adulyadej as a national gift tied to his 50th year on the throne.
The stone was discovered in the Premier Mine in South Africa in the mid 1980s and arrived on an unusual path from the mine to its current place in the Thai royal collection. The rough weighed roughly 755 carats when found and was subsequently reduced and shaped into a fire rose cushion cut. The finished gem, cut to 545.67 carats, was the product of several years of cutting and polishing.
A syndicate of Thai businessmen purchased the polished stone from De Beers and arranged for it to be presented to the Thai monarch as a tribute marking the monarch’s Golden Jubilee. The presentation process included ceremonial blessings and international exhibitions before the diamond entered the royal holdings in the late 1990s.
Gemological context
The Golden Jubilee overtook the long held second place among famous large cut stones and sits above the Cullinan I in weight. A technical review of historical large diamonds places the Golden Jubilee ahead of the Cullinan I by more than 15 carats when comparing finished weights. The Gemological Institute of America has discussed that the 545.67 carat weight of the Golden Jubilee surpassed the Cullinan I in size after its cutting was completed.
The gem is classified as a fancy yellow brown diamond and was given its design by an expert cutter whose work aimed to maximize the best optical qualities available in the rough. The shape and finish reflect deliberate choices made by cutters who spent years on the stone and who used specialized techniques developed for other high profile stones. The Golden Jubilee’s color and weight set it apart from most museum and crown collection pieces, which are more often clear or near colorless.
Public display and provenance
Before its formal acceptance by the royal household the diamond was exhibited internationally. It was shown at trade centers and jewelry exhibitions and received religious blessings at major faith centers, a sequence intended to honor the symbolic purpose assigned by its donors. After arrival in Thailand the gem became part of the royal regalia and has been displayed for public viewing within the royal museum complex. Official descriptions of the stone and museum listings identify the Golden Jubilee as a standing exhibit in Bangkok.
Value and cultural significance
Estimations of monetary value for a stone of this size vary widely and depend on market conditions, rarity of color, and provenance. Independent industry estimates and public commentary have placed the value in a range that reflects both gemological considerations and added cultural worth tied to its role as a royal gift. The decision by a group of private citizens to purchase and donate the diamond reflected a particular intention to mark a national milestone and to reinforce links between business elites and the monarchy.
Why the Golden Jubilee remains notable
Large diamonds are rare and their histories often trace global networks of mining, cutting, trade and ceremonial display. The Golden Jubilee is notable for how its physical scale intersects with ceremony. It became a focal object during a national anniversary, went through a public blessing process, and now forms a visible element in a modern monarchy’s public heritage. That trajectory helps explain why the stone remains extensively referenced in museum guides, record listings, and industry discussions about the world’s largest polished gems.
The presence of the Golden Jubilee in Thailand’s royal collection underscores how high value objects can function beyond monetary terms. They serve as instruments of diplomacy, national imagery, and private commemoration. Visitors who view the gem encounter a piece shaped by decades of technical work and by specific social choices that moved the stone from a South African mine to a ceremonial role in Southeast Asia.
Museum curators and gem specialists continue to point to the Golden Jubilee as a case study in large scale gem cutting and in the ways modern states treat extraordinary objects. The stone’s physical presence will likely continue to draw attention from scholars, collectors and tourists interested in the intersection of geology, craft and political symbolism.
