The Bayan Obo mine located in the Inner Mongolia region of China is the world’s biggest rare earth element (REE) mine both by recoverable reserves and production. It accounts for more than 40% of the total known REE reserves in the world and nearly half of the global rare earth production.
Owned and operated by Chinese state-owned Baogang Group or the Baotou Iron and Steel Group, the rare earth mine has been producing since 1957.
The iron ore reserves at Bayan Obo were discovered in 1927 while the rare earth elements were discovered in 1935.
The Bayan Obo deposit is estimated to contain in excess of 100 million tonnes (Mt) of proven rare earth reserves which account for more than 80% of the total rare earth reserves in China.
Apart from iron ore, the giant open-pit mine produces 15 kinds of rare earth minerals that are used in diverse areas including oil refining, permanent magnets, renewable energy technologies, as well as in metallurgical, polishing, and defence applications.
Location and geology
The Bayan Obo mine site is spread over 48km2 in the Inner Mongolia Autonomous Region, on the northern edge of the North China Kraton, approximately 150km north-west of Baotou.
Bayan Obo is a massive polymetallic rare earth element (REE) and iron ore deposit of hydrothermal origin.
Mineralogy of the Bayan Obo ore
The Bayan Obo ore consists of more than 100 minerals with the principal rare earth mineral ores being monazite and bastnaesite.
The rare earth oxides and niobium are produced as by-products of the iron ore mining operation at Bayan Obo. The ore also contains certain radioactive elements.
The ore contains a total of 15 rare earth elements with three main light rare earth elements lanthanum (La), cerium (Ce), and neodymium (Nd) found in higher percentages.
The iron minerals found in the ore include magnetite and hematite. The Bayan Obo ore also contains several niobium minerals including fergusonite, aeschynite, and columbite.
The main gangue minerals found in the Bayan Obo ore are quartz, apatite, dolomite, and fluorite.
Mining at Bayan Obo
The open-pit mining method is employed for extracting ore at Bayan Obo. The mine complex comprises three open-pits namely the Main pit, East pit and the West Pit, as well as milling and tailings storage facilities and waste rock dumps on-site.
The Main pit measures 1,520m-long and 1,080m-wide, while the East pit is 1,400m-long and 1,020m-wide.
The West pit that measures 4.6km long and up to 1.2km wide is the biggest among the three pits.
The ore material from the mine site is sent to Baotou for processing. Located approximately 150km south of Bayan Obo, Baotou is known as the rare earth capital of China. Bayan Obo and Baotou are connected both by rail and road.
Baotou is home to iron and steel refineries as well as rare earth processing facilities for the production of rare earth oxides, chlorides, carbonates as well as different alloy products.
The rare earth elements from the ore are separated and purified through magnetic separation, flotation, and hydro-metallurgical techniques including leaching, acid baths, and solvent extraction.
The light rare earth elements and heavy rare earth elements are produced by molten salt electrolysis and vacuum metallothermic reduction methods respectively.
China Northern Rare Earth (Group) High-Tech Co., a subsidiary of Baogong Group, is the owner and operator of the processing facilities at Baotou. It is the biggest supplier of rare earth in the world.
China’s dominance in rare earth production
China is the biggest producer of rare earth elements in the world. The country produced more than 60% of the world’s total rare earth production in 2019. According to the US Geological Survey estimates, China’s REE production increased from 120,000t in 2018 to 132,000t in 2019. The global REE production increased from 190,000t in 2018 to 210,000t in 2019.
The US that produced 26,000t of REE in 2019 compared to 18,000t in 2018 is the world’s second-biggest rare earth producer. The Mountain Pass rare earth mine is currently the only operating rare earth mine in the US.
Apart from Bayan Obo, the other rare earth mines in China include Daluxiang (Dalucao) and Maoniuping in the Sichuan province, as well as the ion-adsorption REE-bearing clay deposits in Jiangxi, Hunan, Fujian, Guangdong, and Guangxi provinces.