Mir Mine also called Mirny Mine is a former open pit diamond mine located in Mirny, Eastern Siberia, Russia. At the time of its closing in 2004, the mine was 525 meters deep and 1,200 meters across making it the second largest excavated hole in the world, after Bingham Canyon Mine. The hole is so big that airspace above the mine is closed for helicopters because of incidents in which they were sucked in by the downward air flow.

Mining began on 1957, in extremely harsh climate conditions. The Siberian winter lasted seven months which froze the ground, making it hard to mine. During the brief summer months, permafrost would become mud turning the entire mining operation into a land of sludge. Buildings had to be raised on piles, so that they would not sink. The main processing plant had to be built on better ground, found 20 km away from the mine. The winter temperatures were so low that car tires and steel would shatter and oil would freeze. During the winter, workers used jet engines to burn through the layer of permafrost or blasted it with dynamite to get access to the underlying kimberlite. The entire mine had to be covered at night to prevent the machinery from freezing.

During its peak years of operation, the mine produced 10 million carats of diamond per year, of which a relatively high fraction (20%) were of gem quality. This worried De Beers company, which at that time was distributing most of the world's diamonds. The company was forced to buy larger and larger shipments of high-quality Russian diamonds in order to control the market price. For De Beers, Mir was a puzzling mystery. The mine’s enormous output was not consistent with the relatively small size of the mine. By the 1970s, when the Mir should have been producing smaller and smaller quantities of diamonds, the Soviets were producing an increasing quantity of gem diamonds. Finally, in 1976, De Beers requested a tour of the Mir mine to satisfy their curiosity. Permission was granted, but the Russians kept delaying the visit and by the time the team of delegates reached the Mir mine, their visas were about to expire, so that they could only have 20 minutes at the Mir mine. The visit did little to shed light on the mystery of the Mir’s diamond production.

After the collapse of the USSR, in the 1990s, the mine was operated by a few local companies until 2004 when the mine was permanently closed.

Sources: Wikipedia, Abazias