The Williamson Diamond Mine is located in Tanzania; it was the first major diamond mine founded outside South Africa. Also called the Mwadui Mine for its location, it is about 160 kilometers south of Mwanza on the shores of Lake Victoria.
Some of the most impressive stones removed from the mine include a 54-carat flawless pink diamond that was given to then-Princess Elizabeth and Prince Philip for their wedding in 1947, and a 388-carat diamond found in 1990. The mine continues to be a source of rare pink diamonds.
The mine operates as an open-pit mine and reaches about 90 meters at its deepest point; its average is some 30 to 35 meters deep. Around 1,000 people are employed by the mine.
The Williamson Diamond Mine was begun in 1940 by a Canadian geologist named John Williamson. It has been in continuous operation since its inception, which makes it one of the oldest continuously operating diamonds mines in the world.
The mine was originally owned by John Williamson, but the Tanzanian government later nationalized it. Today, most of the mine is owned by Petra, who bought its 75% share from De Beers in 2008; the remainder is still owned by the government.
The Williamson mine is located along the largest exploitable diamond-bearing kimberlite pipe in the world. It is 1.46 square kilometers in area on the surface. According to exploration by De Beers, the pipe is pyroclastic kimberlite, as opposed to hypabyssal kimberlite as was originally thought. That means that the pit might be able to be dug to as deep as 350 meters.
While the mine once produced ore grade of about 30 carats per hundred tons, its production is now down to some 6 carats per hundred tons. The mine’s peak production was in 1966, when it yielded over 900,000 carats; nowadays, Williamson Diamond Mine averages about 100,000 carats annually. In 2010, the diamonds from Williamson fetched an average of $157 per carat.
The mine has yielded about 20 million carats and is thought to contain an additional 40 million carats.
