Williamson Diamond

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Origin of name

The Williamson diamond gets its name from Dr. John Williamson, the renowned Canadian Geologist, who discovered the diamond in 1947 in his own mine in Tanzania (Tanganyika), which is known as the Williamson diamond mine or Mwadui diamond mine, and subsequently presented it in the rough state, as a wedding gift to Princess Elizabeth (later Queen Elizabeth II) in the same year.

Characteristics of the diamond

The Williamson diamond  is a pale pink, flawless (exact color and clarity grades not known), round brilliant-cut diamond, weighing 23.56 carats. In the list of famous pink diamonds below Williamson's diamond occupies the 9th position.

List of famous pink diamonds

S/No Name

Carat Weight


1 Darya-i-Nur 186 light pink
2 Nur-ul-Ain 60 light pink
3 Steinmetz pink 59.60 fancy vivid pink
4 Shah Jahaan 56.71 light pink
5 Agra 32.34 fancy light pink
6 Pink Sunrise 29.79 fancy pink
7 Rose of Dubai 25.02 fancy pink
8 Mouawad Lilac 24.44 fancy purplish pink
9 Williamson 23.56 fancy pink
10 Graff Pink Orchid 22.84 fancy purplish pink
11 Mouawad Pink 21.06 fancy pink
12 Hortensia 20.00 light orange pink
13 Graff Pink Supreme 10.83 fancy pink
14 Conde Pink 9.01 light pink

Williamson diamond is a Type IIa diamond, free of nitrogen and other impurities. They are said to be chemically pure diamonds. Normally these diamonds have structurally perfect crystals and are absolutely colorless. They constitute about 1-2 % of all naturally occurring diamonds. However a small percentage of these diamonds have undergone plastic deformation in the crystal structure, by the twisting and bending of crystal units, which change the absorption spectrum of the diamond causing rare fancy colors such as pink, red, purple and sometimes brown.

The occurrence of pink diamonds is much less than 0.1 % of all naturally occurring diamonds. In the Argyle mines of Western Australia, the main source of pink diamonds in the world today, a statistical analysis has shown that only a single carat of pink diamond is produced for every 1,000,000 carats of gem-quality rough diamonds. This works out to an unbelievably low occurrence of 0.0001 %.

Another interesting feature of pink diamonds seen in the above table, is that except for the first diamond, the Darya-i-Nur, all other diamonds are less than 100 carats in weight. In fact most of the diamonds are around 20 to 30 carats in weight. In the Argyle diamond mines, the average size of pink diamonds produced is much less than this, and is only about 1.0 carat in weight. Thus pink diamonds have a restricted size as compared to white and yellow diamonds.


The Williamson diamond was the first notable diamond to be produced in the Williamson diamond mine, in Tanzania, after its discovery in 1940, by Dr. John Williamson, the Canadian Geologist. The rough diamond weighed 54 carats, and was presented to Princess Elizabeth and Prince Philip, upon their wedding in 1947. The diamond was cut and polished by Briefel and Lemer of London in 1948. The Princess then commissioned the jewelry firm of Cartier's to design a flower-shaped brooch for her with the 23.56-carat Williamson diamond as the centerpiece. The brooch was designed by Frederick Mew of Cartier's in 1952.

Williamson Diamond Mine - Tanzania.

Diamond mining in Tanzania started in the 1930s, with several small scale mines beginning operations, but production was insignificant. Then in 1938, the operators of the Mabuki diamond mine invited Dr. John Williamson, a Canadian Geologist to conduct a geological survey of the area, with a view of identifying prospective diamond mining areas. In 1940, Dr Williamson, positively identified a gem-bearing Kimberlite pipe, about 160 Km south of the town of Mwanza, on the shores of Lake Victoria, in the Shinyanga region of Tanzania. Dr. Williamson named the mine, Mwadui mine, after a local chief of the area, but subsequently the mine became popularly known the Williamson mine. The diamond-bearing volcanic pipe had a surface mining area of 1.46 Sq. Km. and it was one of the largest economically exploitable diamond-bearing volcanic pipe in the world.

Dr Williamson began the exploitation of the mine as an open pit mine,  but soon encountered difficulties in procuring the necessary funds and equipment, due to the outbreak of the second world war. But, immediately after the war, he was able to invest sufficient funds for the development of the mine, and by 1950 the Williamson diamond mine became the first significant diamond mine in Tanzania, and outside South Africa. Dr. Williamson installed state-of-the-art equipment in his mine and was responsible for introducing several technical innovations in diamond mining.

Production output in the mines were quite attractive in the 1950s and 1960s, when the average output was between 500,000 and 750,000 carats per year. with a peak production of 925,000 carats in 1966. But, today production levels have dropped to an average of 300,000 carats per year. The mine that is still under production, has produced a total of around 20 million carats of diamonds since it's inception. Presently the mine employs about  1,100 workers, and the depth of the mine is about 90m (300 ft).

Dr John Williamson died in 1958, at the age of 50 years, and immediately after his death, his heirs sold the mine to a joint company of De Beers South Africa and the Colonial Government of Tanganyika, for a sum of £ 4 million sterling. Tanganyika became independent on Dec 9, 1961, with Julius Nyerere as Prime Minister. In 1964, Tanganyika formed a union with neighboring island State of Zanzibar, and emerged as a sovereign republic known as the United Republic of Tanzania, with Julius Nyerere as President and Sheik Abeid Amani Karume the president of Zanzibar, as the Vice President. In 1971 almost 10 years after the independence of Tanganyika, the Williamson diamond mines were nationalised. From 1971 to 1994 the mine was managed by the Government of Tanzania, but there was serious deterioration in the mines performance attributed to inadequate capital investment, a bloated labour force, loss of skilled, foreign management and engineering staff, and a decrease in the grade of the ore. In 1994 the Government of Tanzania, re-invited De Beers of South Africa to invest in the mine, and De Beers bought over 75 % of the shares of the mine, 25 % being retained by the Government. De Beers has now taken over the management of the mine, and has improved the efficiency of the mine, by reducing the workforce, investing in modern equipment and technology, and bringing in  foreign expertise for operations of the mine and further exploration. Studies have already been concluded by the company to look into the possibilities of extending the operations of the mine, by going further deep into the diamond-bearing Kimberlite pipe, extending the life of the 67-year old  diamond mine.

Back to Famous Diamonds of the World- 2

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