Western open pit mining was carried out in 1901. In 1914, it was converted to open-pit mining. It is a large-scale coal mine with a history of 100 years. The west open pit is 6.6 kilometers long and 2.2 kilometers wide from north to south. The total pit area is 14.52 square kilometers and the vertical depth of mining is 400 meters. It is the largest open pit mine in Asia.