Kasai is a region of the Democratic Republic of the Congo whose name attaches to the Kasai river and its tributaries, and to the historical mining province established under Belgian colonial administration. The Kasai basin has been a major source of alluvial diamonds for over a century, with both industrial and artisanal mining operating across an extensive geographical area and producing a substantial share of the country's overall diamond output, although under conditions that have made the region's product subject to particular regulatory scrutiny under Kimberley Process and OECD due-diligence frameworks.

Geological setting

The diamonds of the Kasai region derive primarily from kimberlite intrusions in the broader Kundelungu and Kasai cratonic terrains, with diamonds released through weathering and transported by the dendritic Kasai-Sankuru-Lulua river network into alluvial concentrations. Most of the Congolese alluvial production has come from these alluvial deposits rather than from primary kimberlite mining, with very limited industrial extraction of primary kimberlite ore and large-scale artisanal working of secondary alluvium.

The Mbuji-Mayi area in the southern Kasai region hosts the Bushimaie kimberlite pipes worked industrially by the Congolese state company MIBA (Société Minière de Bakwanga). MIBA's production has fluctuated heavily across the past five decades with shifting ownership, financing and operational continuity, and the company's industrial output has been intermittent. Beyond MIBA's footprint the region's diamond economy is overwhelmingly artisanal, with hundreds of thousands of diggers working alluvial gravels along the river systems.

Production and trade

Congolese diamond production includes both gem-quality and industrial material, with the gem-quality fraction running through Tshikapa, Mbuji-Mayi and Kinshasa export channels into the international market. Antwerp has historically been the principal export destination, with secondary flows through Tel Aviv, Mumbai and Dubai. The country has been a Kimberley Process participant since the scheme's inception in 2003, with all official export shipments accompanied by Kimberley Process certificates.

The artisanal sector has been a focus of due-diligence concerns under the OECD's guidance for responsible supply chains in conflict-affected and high-risk areas. Documentation of chain-of-custody from artisanal digger through cooperative or buyer to export point is challenging, and the region has appeared repeatedly in independent investigations of diamond-supply integrity. Reputable buyers seeking Congolese material work through certified channels and through the limited industrial production rather than through unverified artisanal supply.

Trade context

For the working trade Kasai is most useful as a regional descriptor rather than a per-stone provenance call. Country-of-origin attribution to the DR Congo is supported by Kimberley Process documentation but does not on its own answer due-diligence questions about artisanal versus industrial source. Large gem-quality stones from MIBA-area production reach the international market under documented provenance, while smaller and irregular stones from artisanal sources generally enter the trade pool without source-level identification.

The region's significance is as one of the principal alluvial diamond provinces of central Africa, alongside the Angolan Lunda district to the south and the Central African Republic deposits to the north. Kasai material has been part of the global diamond stream for over a century and continues to supply a meaningful share of world rough.