The Banjarmasin Diamond – From Borneo to Amsterdam
Weighing 38.23 carats, the Banjarmasin Diamond is one of the largest diamonds found in Southern Borneo. To briefly summarize the history of this region (today South Kalimantan, Indonesia): The Netherlands had been occupying the territory since 1815, it became a Dutch protectorate in 1891 (as part of the Dutch East Indies), was occupied by the Japanese during World War II, from 1941-45, and achieved its independence when Indonesia itself became independent in August 1945.
You will know from my history of diamonds that Borneo was the only other territory besides India where diamonds were mined in antiquity (diamond mining became largely known in Europe in the 17th century). Therefore it is an important source of diamonds, albeit on a much smaller scale than India.
Much controversy has surrounded the history of the Banjarmasin Diamond. As a rough gem of in the excess of 70 carats, it was considered to be of great personal value to Sultan of the territory and his family. The death of the Sultan marked the beginning of the 6-year Banjarmasin War in 1859. In 1860 the Dutch dissolved the Sultanate altogether and the regalia of the Sultan were sent Jakarta. In late 1861 the Banjarmasin Diamond was taken (some say forcefully confiscated) and sent to Amsterdam, where the intention was at first to gift it to King William the III. After several attempts to sell the gem or offer it to a museum failed, it was finally, in 1902 (as a cut 38.23 carat diamond), given to the Rijksmuseum in Amsterdam, where it is still on display today.
The Banjarmasin Diamond was cut in 1870 by Coster Diamonds in Amsterdam, the same company which had cut the famous Star of the South and the legendary Koh-i-Noor (see my introduction of famous diamonds). It is cut in a cushion shape (see above): a comment must be made as to the great reduction in weight from its original 70+ carats to a little more than 38 (an almost 50% reduction!) The reason for this could possibly be due to imperfections in the stone as well as it reportedly having a less-than-desired brilliance and yellowish tint; the cutter would have taken the most brilliant and flawless part of the rough stone so the resulting cut gem was as perfect as could be obtained from the rough original.
[From an article in the Journal of Gemology Vol. 38 (No.7) 2023 by Suzanne van Leeuwen and J. C. (Hanco) Zwaan]