Historic Diamond Fields & Mines in Sierra Leone

Kono District — Koidu & Yengema (alluvials and kimberlite)

Sierra Leone’s diamond story began in 1930 with alluvial finds in Kono District. The colonial-era Sierra Leone Selection Trust (SLST) opened large alluvial operations at Koidu/Yengema in the 1930s, and the district later hosted one of West Africa’s best-known primary deposits: the Koidu Kimberlite Project (pipes and dykes). Historic alluvials along tributaries near Koidu produced giants such as the Woyie River stones, while today’s mining centers on kimberlite at Koidu (Octéa/Koidu Limited) alongside artisanal activity. Sources: GIA Africa history; SLST background & early production notes; Koidu Kimberlite Project overview.

Tongo / Tonguma — Kimberlite dyke field (Kenema/Kono)

South-southeast of Koidu, the Tongo/Tonguma field comprises narrow but high-grade kimberlite dykes long recognized for gem-quality output. Alluvial mining at Tongo began in the 1950s; modern work targets the dyke system itself, with development programs advancing intermittently in the 2010s–2020s. Sources: Mindat locality summary; Mining-Journal history of Tongo alluvials and dyke development.

Sewa & Woyie Rivers — Classic alluvial fields

The Sewa and Woyie river systems fed major alluvial workings from mid-century onward, yielding some of the country’s most famous finds. The Woyie River near Koidu produced a 770 ct rough in 1945 (then the largest alluvial diamond known), later cut into 30 stones including the “Victory” diamond. The Sewa and neighboring drainages remain emblematic of Sierra Leone’s alluvial heritage. Sources: Wikipedia “Woyie River diamond”; Cape Town Diamond Museum note on Woyie/Victory.

Sierra Leone’s Most Historic & Largest Diamonds

Star of Sierra Leone

Rough: 968.9 ct, recovered Feb. 14, 1972 from Diminco alluvial workings near Koidu. Cut: initially a 143.20 ct emerald-cut, later recut into 17 stones (total 238.48 ct), of which 13 were flawless; the largest polished is a 53.96 ct pear. Notes: Purchased by Harry Winston; among the largest gem-quality and the largest alluvial diamond ever recovered. Sources: Wikipedia “Star of Sierra Leone”; Christie’s lot essay; GIA/trade summaries.

Woyie River Diamond → “Victory”

Rough: 770 ct, recovered Jan. 6, 1945 from the Woyie River near Koidu; at the time, the largest alluvial diamond known. Cut: fashioned in London into 30 gems (total 282.36 ct); the largest, the Victory Diamond, is a 31.34 ct D-color, VVS2, Type IIa step-cut. Sources: Wikipedia “Woyie River diamond”; Sotheby’s Victory Diamond note; BBC/industry summaries.

Peace Diamond

Rough: 709 ct alluvial diamond recovered March 2017 at Koryardu (Koidu area) by a team led by Pastor Emmanuel Momoh. Sale: auctioned in Dec. 2017 for $6.5 million, purchased by Graff, with proceeds routed through official channels to benefit local communities. Sources: Wikipedia “Peace Diamond”; Africanews sale report; Graff & PeaceDiamond.com notes.

Summary

Sierra Leone’s diamond legacy runs from mid-century alluvial giants on the Sewa/Woyie to modern kimberlite mining at Koidu and prospective dyke operations at Tongo/Tonguma. Landmark stones—the 968.9 ct Star of Sierra Leone, the 770 ct Woyie River “Victory,” and the 709 ct Peace Diamond—anchor the country’s place in diamond history while today’s projects balance primary mining with artisanal traditions. Primary references: GIA Africa history; mine and auction records cited above.

Datasets: U.S. Geological Survey, Major Mineral Deposits of the World, Open-File Report 2005-1294. Data portal