Borneo has produced diamonds for centuries, almost all of them from river gravels in the Indonesian provinces of Kalimantan. The deposits are small by world standards, and mining has mostly been done by hand. Borneo is still one of the oldest diamond sources outside India, and its local panning traditions have survived into modern times. The two best-known areas are Cempaka in South Kalimantan and Landak in West Kalimantan.
A long history of production
Diamonds were being found in Borneo well before European traders arrived in Southeast Asia. Some writers suggest that Borneo diamonds were traded across the region more than a thousand years ago, though early records are thin. Local sultanates on the island controlled diamond-bearing land and claimed the best stones.
European interest grew from the 17th century. Dutch traders, and at times the English, sought Borneo diamonds through local rulers, and diamonds passed through ports on the island's coasts. In the 19th century the Dutch colonial government extended its control over the diamond districts of southern and western Borneo. Production then was modest compared with India, and later with Brazil and South Africa, but it continued without long interruption. The context for this trade is on the page on the history of the diamond trade.
Where the diamonds are
Borneo's diamonds have been found almost entirely in alluvial deposits: river gravels, terraces and old buried channels. The two main districts are:
- Cempaka (sometimes written Chempaka), near the town of Banjarbaru and the city of Martapura in South Kalimantan, below the Meratus Mountains.
- Landak, in West Kalimantan, inland from the coast near the provincial capital Pontianak.
Smaller occurrences are scattered elsewhere on the island. The source of the diamonds has puzzled geologists. Borneo is not an ancient stable craton like southern Africa or Siberia, and no productive kimberlite or lamproite pipes have been found. Researchers have proposed that the diamonds were carried in by other geological processes, possibly linked to the movement of crustal blocks or to ophiolites, slices of oceanic crust and mantle pushed onto the edge of the continent. The question remains open. The general geology of diamond deposits is covered on the diamond geology page.
Traditional panning
Most Borneo diamond mining has been done by small groups of local miners using simple tools. A typical operation follows a sequence:
- Miners dig a pit or shaft through the overburden, sometimes many meters deep, to reach the diamond-bearing gravel layer.
- They haul up the gravel by hand or with small pumps.
- They wash it in a wide, conical wooden pan called a "linggangan," swirling water to wash away light material.
- Heavy minerals, including gold and diamonds, settle at the bottom of the pan, where the miner picks them out.
Gold is often found in the same gravels, and many miners recover both. At some sites crews use gasoline-powered pumps to spray water at gravel banks and pump slurry over sluices. These methods resemble those described for alluvial deposits on the page about how diamonds are mined.
Work is often organized in small cooperatives or family groups. A find is shared between the diggers, the landowner and the person who financed the pumps or fuel, under local customs. Martapura became the main local trading center, with a market for rough and polished diamonds and other gemstones.
Large Borneo diamonds
Borneo has produced a few large stones. The best known modern find is the Trisakti, a diamond of about 166.75 carats found at Cempaka in 1965 by local miners. It was handed over to the Indonesian state and later cut. Older stories describe a very large stone held by the Sultan of Matan in West Borneo, sometimes called the Matan diamond, but its actual nature and weight have been questioned, and it may not have been a diamond at all.
Borneo diamonds have also included colored stones, such as yellow, pink and blue diamonds, in small numbers. Colored diamonds are covered on the page on fancy colored diamonds.
Industrial attempts
Over the 20th century several companies tried to mine Borneo's deposits on a larger scale, using dredges or mechanized plants. Several projects in South Kalimantan were proposed or tried, especially in the Cempaka area, but none grew into a large, long-running operation. Small-scale traditional mining has remained the main form of production, and its scale has varied with the economy and local regulations.
Small-scale mining in Kalimantan has also raised environmental concerns, including stripped land, silted rivers and mercury use by the gold miners who work the same gravels. These problems resemble those found at artisanal diamond fields in West Africa, described for Liberia and in the page on conflict diamonds, though Borneo's diamonds have not been tied to armed conflict.
Borneo diamonds in the world market
Borneo has always been a minor source by volume. Many of its stones are sold and cut locally, especially in Martapura, which has a long tradition of cutting and polishing and supplies Indonesian buyers. Indonesia joined the Kimberley Process to keep its rough exports in the certified trade. For a comparison with the major producers, see diamond mines of the world.
Frequently asked questions
Where are diamonds found in Borneo?
Most come from alluvial gravels in Kalimantan, the Indonesian part of Borneo. The main areas are Cempaka in South Kalimantan and Landak in West Kalimantan.
How are diamonds mined in Borneo?
Most mining is done by small groups digging pits and washing gravel in wooden pans called linggangan. Some crews use pumps to spray and sluice gravel.
What is the largest diamond found in Borneo?
The best documented large stone is the Trisakti, about 166.75 carats, found at Cempaka in 1965.
Where do Borneo's diamonds come from geologically?
Their source is uncertain. Borneo lacks the ancient craton and kimberlite pipes typical of major diamond regions, and geologists have proposed several alternative explanations.