The Golden Jubilee Diamond, a 545.67 carat (109.13 g) brown diamond, is the largest cut and faceted diamond in Southeast Asia and the world. It outweighs the Cullinan I by 15.37 carats (3.07 g).
The Golden Jubilee Diamond was discovered in the Premier Mine, which is also the origin of the Cullinan diamond (1905) and other notables such as the Taylor–Burton (1966) and the Centenary (1986). Cullinan I, also known as the Great Star of Africa, had held the title of the largest cut and faceted diamond since 1908.
First known as the “Unnamed Brown”, the Golden Jubilee Diamond was cut from a large brown diamond of 755.5 carats (151 g), found in the prolific blue ground of the Premier Mine in South Africa in 1985.
The unnamed diamond was brought to Thailand by the Thai Diamond Manufacturers Association to be exhibited in the Thai Board of Investment Exhibition in Laem Chabang and was selected to herald De Beer’s centennial celebrations in 1988.
The Golden Jubilee was purchased from De Beers by a group of Thai businesspeople led by Henry Ho in 1995.
It was arranged for the diamond to be given to King Bhumibol as a gift from the people to celebrate the 50th anniversary of the King’s ascent to the throne. The diamond was named the Golden Jubilee, and was received by the King’s daughter, Princess Maha Chakri Sirindhorn, on his behalf in 2000.
The diamond is now on display in the Royal Museum at Pimammek Golden Temple Throne Hall in Bangkok as part of the crown jewels.
The value of the Golden Jubilee diamond is believed to range between $4 and $12 million USD. If sold at auction, it is likely that this stone would fetch a significantly higher price, such additional value gained from affiliation with prominent individuals (Thailand royalty).
According to en.wikipedia.org