gems, diamond, Borneo, Kalimantan, Indonesia

The island of Borneo, one of the oldest known but least documented diamond sources, has a history of mining primarily in the western region of present-day Kalimantan. Recent activity, however, has shifted to the alluvial deposits in the southeast. A progress report on the first bulk sample pit in this area revealed that a significant concentration of diamonds lies beneath the center of the Danau Seran swamp. While traditional hand-mining methods remain common, the bulk sampling operation has employed far more advanced techniques. Nearly all recovered diamonds are gem quality, though they are generally small, averaging about 0.30 ct. The southeastern region of Kalimantan holds excellent future potential for diamond production.