Latitude & Longitude (WGS84):	3° 31' 1'' South , 33° 36' 29'' East
Latitude & Longitude (decimal):	-3.51722,33.60806
GeoHash:	G#: kxrguz8ws
Owned/operated by:	Petra Diamonds Ltd (75%)
Locality type:	Mine
Köppen climate type:	Aw : Tropical savanna, wet

Williamson is an open pit operation based upon the 146 hectare Mwadui kimberlite pipe, which is the world’s largest economic kimberlite to have seen continuous mining.

The Williamson mine was discovered in 1940 by Dr John Williamson, a Canadian Geologist, and is the largest economic primary diamond deposit to be in continuous production. Williamson has been successfully mined for over 70 consecutive years, and as such holds the record for the world’s longest running uninterrupted diamond mining operation.



By the 1950s the mine had developed into a successful operation with equipment that was state-of-the-art for its time and a labour force of several thousand. The mine was closely managed by Dr. Williamson until his death in 1958. During this period production was predominantly from near-surface eluvial deposits that had undergone significant secondary diamond concentration, with grades that ranged from 30 cpht to 100 cpht and an annual production approaching 1 Mcts.

In 1958, the mine was sold to an equal partnership between De Beers and the colonial Government of Tanganyika. De Beers operated the mine until 1973. Tonnages and carats produced increased dramatically during this period, but grades dropped to well below 30 cpht as the open pit entered primary RVK (resedimented volcaniclastic kimberlite) material underneath the near-surface zone of eluvial enrichment.

From 1974 to 1993, the mine was operated by STAMICO (the Tanzanian State Mining Organisation). Grades varied between 5 and 12 cpht and diamond output fell dramatically relative to the previous 15 years to approximately 70,000 carats per annum. In 1993 De Beers returned to Williamson as operators, together with a recapitalisation and ownership restructuring. Production increased to approximately 195,000 carats per annum to 2005. De Beers announced it would be selling its 75% interest to Petra Diamonds in November 2008, and the acquisition of Williamson in February 2009.

Williamson is renowned for ‘bubblegum’ pink diamonds, including the Williamson Pink, which is considered one of the finest pink diamonds ever discovered. It was found in October 1947 weighing 54 carats in the rough. The mine, then owned by the Canadian geologist and royalist Dr John Williamson, gave the diamond to Princess Elizabeth in 1947 as a wedding present. It was cut into a 23 carat round brilliant and set as the centre of a brooch in the form of a jonquil flower, designed and set by Cartier in 1953 – see our Diamond Heritage.

The mine also produces beautifully rounded white diamonds of high quality.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Neoarchean - Mesoarchean 2500 - 3200 Ma ID: 3308162	Age: Archean (2500 - 3200 Ma) Lithology: Volcanic-sedimentary Reference: Thiéblemont, D. (ed.). New edition of the 1:10,000,000 geological map of Africa. CGMW-BRGM. [190]
Archean 2500 - 4000 Ma ID: 3186108	Archean crystalline metamorphic rocks Age: Archean (2500 - 4000 Ma) Lithology: Crystalline metamorphic rocks Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

External Links