Mirny Diamond Mine is the second largest man made hole in the world…

The Mir mine, also known as the Mirny mine, is an abandoned open pit diamond mine in Mirny, Russia, in Eastern Siberia. The mine is 525 meters (1,722 feet) deep and 1,200 meters (3,900 feet) in diameter, making it the world’s second-largest excavated hole after the Bingham Canyon Mine.

The diamond-bearing deposits were discovered on June 13, 1955, by Soviet geologists Yuri Khabardin, Ekaterina Elagina, and Viktor Avdeenko during the enormous Amakinsky Expedition in Yakut ASSR. They found kimberlite, a volcanic rock associated with diamonds. After many futile flights in the 1940s and 1950s, this was Russia’s second kimberlite success. (The Zarnitsa mine was the first to open in 1954.) In 1957, Khabardin was given the Lenin Prize, one of the highest accolades in the Soviet Union, for this discovery.

atlas Obscura

The mine’s construction began in 1957, amid the midst of extremely severe environmental conditions. For seven months of the year, the soil remained frozen, making mining difficult. During the brief summer months, the earth turned to mush. To avoid sinking, buildings had to be erected on piles. The principal processing plant had to be built on  better ground found 20 kilometers away from the mine. Winter temperatures were so low that automotive tires, steel, and oil froze. To get access to the underlying kimberlite, workers melted and dug out the permafrost using jet engines or blasted it with dynamite throughout the winter. The entire mine had to be covered at night to protect the machinery from freezing.

The mine produced 10,000,000 carats (2,000 kg) of diamond per year in the 1960s, with a comparatively high percentage (20%) of gem quality.

The uppermost layers of the mine (down to 340 meters) exhibited a very high diamond concentration of 4 carats (0.80 g) per tonne of ore, with a high gem-to-industrial stone ratio. Near the pit bottom, the yield fell to around 2 carats (0.40 g) per tonne, and the annual production rate was decreased to 2,000,000 carats (400 kg).

The mine’s largest diamond, measuring 342.5 carats (68 g), was discovered on December 23, 1980, and was named “26th Congress of the CPSU” (Russian: XXVI сeд C). When the pit bottom became inundated in the 1990s, the mine operation was interrupted at a depth of 340 m, but it was resumed in the late 1990s.

atlas Obscura

The rapid growth of the Mir mine had frightened De Beers, which dispersed the bulk of the world’s diamonds at the time. De Beers sought to know as much as it could about Russian mining achievements because it needed to purchase Russian diamonds in order to control market prices. In the 1970s, De Beers requested permission to inspect the Mir mine. Permission was granted on the condition that Russian experts visit De Beers’ diamond mines in South Africa. De Beers CEO Philip Oppenheimer and chief geologist Barry Hawthorne came in Moscow in the summer of 1976.

A series of meetings and lavish lunches with Soviet geologists, mineralogists, engineers, and mining managers kept them back in Moscow on purpose. Their visas were about to expire when Oppenheimer and Hawthorne got to the Mir mine, so they barely had 20 minutes there. I was able to obtain some crucial information despite the limited time frame. De Beers, for example, was taken aback when the Russians used no water at all throughout the ore processing. Because water would freeze for the most of the year, dry crushing was used instead. De Beers also exaggerated the extent of the mine’s pit.

Mirny Mine during winter. Wikimedia Commons

The Mir mine was the first and largest to be developed in the Soviet Union. Its surface operation lasted 44 years until being shut off in June 2001. Following the demise of the Soviet Union in the 1990s, the mine was controlled by the Sakha diamond business, which boasted annual diamond sales earnings of more than $600 million.

The open pit diamond mine of Mirny in Yakutia. Its depth is 525 meter.

Later, Alrosa, Russia’s largest diamond producer, ran the mine, which employed 3,600 people. Diamond recovery by typical surface mining had long been predicted to halt. As a result, tunnel construction for subsurface diamond recovery began in the 1970s. By 1999, the project had just an underground mine functioning. The abandoned surface main pit’s bottom was covered with a 45-meter-thick debris layer to stabilize it. Based on a drilling exploratory effort to a depth of 1,220 meters, the mine life was anticipated to be 27 years after underground operations began. The Mir mine was permanently closed in 2004.

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