New discoveries of ancient iron smelting sites in Kalimantan

In the past five years, our archaeological research has uncovered evidence of iron making in the Meratus mountains, located upstream of the Barito watershed on the east coast of Kalimantan (Indonesian side of Borneo Island), as well as the Lamandau watershed in southwestern Kalimantan. At these iron industry sites, we discovered slags, ore fragments, tuyere, charcoal, and smelting furnaces. These discoveries provide new insights to address the debates among experts about the emergence and development of iron metal technology in Kalimantan/Borneo Island. Radiocarbon dating conducted at the Cililin 1 Cave site in the Meratus Mountains indicates that the earliest iron ore smelting occurred during the early Christian era (2000–1700 BP). Our excavations also confirm that this ferrous metal technology spread and was practiced towards the east coast and watersheds by the end of the 19th century. The excavated smelting furnaces suggest that direct smelting (bloomery) techniques were used to produce raw iron, based on the furnace shape, charcoal dates, and type of iron slag found. The shape and size of the smelting furnaces in Kalimantan remain consistent from the oldest to the most recent sites. This similarity suggests that there was little technological advancement in iron-making in Kalimantan/Borneo Island between the early AD period and the end of the 19th century. This finding supports the theory that iron technology possibly emerged and developed in Kalimantan several centuries BC.