The rapid development of the Mir mine had worried the De Beers company, which at that time led a cartel that controlled distribution of most of the world's diamonds. De Beers had to buy Soviet diamonds in order to control the market price, and therefore needed to know as much as possible about the Russian mining developments. In the 1970s, in the midst of a proxy cold war in Southern Africa, De Beers requested permission to visit the Mir mine. Permission was granted under the condition that Soviet experts would visit De Beers diamond mines in South Africa. De Beers executive Sir Philip Oppenheimer and chief geologist Barry Hawthorne arrived in Moscow in the summer of 1976. They were intentionally delayed in Moscow by the arrangement of a series of meetings and lavish banquets with Soviet geologists, mineralogists, engineers, and mine managers. When Oppenheimer and Hawthorne finally reached the Mir mine, their visas were about to expire, so that they could only stay for 20 minutes. Even that short time was sufficient to get some important details. For example, the Soviets did not use water during the ore processing at all, which was astonishing to De Beers. The reason was that water would freeze most of the year, and dry crushing was used instead. De Beers also overestimated the size of the mine's pit.