Second largest excavated hole in the world.
“The Mine is so deep that airspace above the mine is closed for helicopters because of a few incidents in which they were sucked in by the downward air flow.”
Mirny Mine is a former open pit diamond mine, now inactive, located in Mirny, Eastern Siberia, Russia. The mine is 525 meters (1,722 ft) deep (4th in the world) and has a diameter of 1,200 m (3,900 ft),and is the second largest excavated hole in the world, after Bingham Canyon Mine.
The diamond-bearing deposit was discovered on June 13, 1955 by Soviet geologists Yuri Khabardin, Ekaterina Elagina and Viktor Avdeenko during the large Amakinsky Expedition in Yakut ASSR. They found traces of volcanic rock kimberlite which are usually associated with diamonds. This finding was the first success in the search for kimberlite in Russia, after numerous failed expeditions of the 1940s and 1950s. For this discovery, in 1957 Khabardin was given the Lenin Prize, which was one of the highest awards in the Soviet Union.
The development of the mine had started in 1957 in extremely harsh climate conditions. Seven months of winter per year froze the ground, which made it hard to mine in the winter, but turned into sludge in summer. Buildings had to be raised on piles, so that they would not sink in summer, and the main processing plant had to be built on a 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, the workers used jet engines to thaw and dig out the 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.
“In the 1960s the mine was producing 10,000,000 carats (2,000 kg) of diamond per year, of which a relatively high fraction (20%) were of gem quality.”