What is the N°1 diamond group?
We can't talk about diamonds without talking about De Beers, the company that single-handedly made the diamond industry what it is today. De Beers was founded by Cecil Rhodes, who also founded the state of Rhodesia which later became Zambia and Zimbabwe. The Rhodes scholarship is also named after him, and funded by his estate.
Rhodes started by renting water pumps to miners during a diamond rush in 1867 at Kimberley, South Africa. He expanded into mines and about twenty years later became the sole owner of all diamond mining operations in the country.
Rhodes built De Beers into a diamond group. De Beers mines diamonds, then handle their sales and distribution through various entities (Today, it's known as the Diamond Trading Company, while previously it was simply called "the syndicate” and the CSO or Central Selling Organization.)
If you want to buy diamonds from De Beers, you've got to play by their rules: diamond are sold in events known as "sights." There are 10 sights held each year, and to buy, you have to be a sight holder (these are usually diamond dealers whose business is to have the stones cut and polished and then resold at diamond clearing centers of Antwerp, New York, and Tel Aviv).