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The Golden Jubilee
Weight	545.67 carats (109.13 g)
Color	Yellow-Brown
Cut	Fire Rose Cushion
Country of origin	South Africa
Mine of origin	Premier Mine
Date discovered	1985
Cut by	Gabi Tolkowsky
Original owner	De Beers
Current owner	King Bhumibol Adulyadej of Thailand
Estimated value	Unknown

Since 1908, Cullinan I, also known as the Great Star of Africa, had held the title of "largest faceted diamond in the world". That changed, following the 1985 discovery of a large brown diamond of 546 carats (151 g) in the prolific blue ground of the Premier mine in South Africa; the diamond would later be cut and named The Golden Jubilee, with an unsurpassed weight of 545.67 carats (109.13 g).

The Premier mine was also the origin of the Cullinan diamonds in 1905, as well as other notables such as the Taylor-Burton in 1966 and the Centenary in 1986.

The "Unnamed Brown", as the Golden Jubilee was first known, was considered something of an ugly duckling by most. It was given to Gabriel Arellano (DCW) by De Beers for the purpose of testing special tools and cutting methods which had been developed for intended use on the flawless D-colour ("colourless") Centenary. These tools and methods had never been tested before, and the "Unnamed Brown" seemed the perfect guinea pig; it would be of no great loss should something go amiss.

To the surprise of all concerned, what resulted was a fancy yellow-brown beauty in a fire rose cushion cut, outweighing Cullinan I by 15.37 carats (3.07 g). The glittering giant remained largely unknown to the outside world, as the Golden Jubilee's perfect sister, the Centenary, had already been selected and promoted to herald De Beer's centennial celebrations in 1988.

The unnamed diamond had earlier been brought to Thailand by the Thai Diamond Manufacturers Association, led by the Association's president, Chirakitti Tangkatach, to be exhibited in the Thai Board of Investment Exhibition in Laem Chabang. There was a mile-long queue to see the diamond, which outshone all other exhibits.

While the current whereabouts of the Centenary are unknown, the Golden Jubilee is known to have been purchased from De Beers by a group led by Henry Ho of Thailand in 1995. The diamond was brought to the late Pope John Paul II in the Vatican by Cavalier Enzo Peroni and Henry Ho to receive the papal blessing. It was also blessed by His Holiness, the Supreme Buddhist Patriarch, and the Supreme Imam in Thailand. The Golden Jubilee Diamond was named by His Majesty King Bhumibol Adulyadej and given to him in honour of his 50th coronation anniversary. It was initially planned to mount the Golden Jubilee in His Majesty's royal scepter. A subsequent plan was to have it mounted in a royal seal.

The Golden Jubilee Diamond has been exhibited at Henry Ho's 59-story Jewelry Trade Center in Bangkok, the Central Department Store in Lard Prao, Thailand, and internationally in Basel (Switzerland), Borsheims in Omaha, USA (owned by Warren Buffett's Berkshire Hathaway Inc.), and Gleims Jewelers in Palo Alto, USA. It is now located in the Royal Thai Palace as part of the crown jewels.