One crack in a wall is all it would take for a dark gray oval that sits across 11 square kilometers of land to create a massive disaster.

Situated just to the west of Baotou, a city in the resource-rich region of Inner Mongolia, the mine dump for Baotou Iron and Steel Group (Baosteel) (CN:600019) is enclosed by a concrete wall that stands 20 meters high. It is one of China’s largest tailings pools, and contains roughly 180 million tons of metal waste powder.

Until recently, few outside the city knew about the mine dump, which was created 60 years ago. The mine has gained attention on reports that the hazardous slurry contains large amounts of rare earths and other minerals, estimated by some to have a total value as high as 80 trillion yuan ($12.8 trillion).

But the dump has attracted its share of negative news as well. At least 4,000 hectares of farmland have already been contaminated by seepage. Over 130 hectares of farmland are unable to support crops or have extremely low output. A number of villagers living nearby have also cited several health problems which they attribute to poor controls on the hazardous waste.

From a distance, the dump looks much like a dark, shining lake. Close-up, a network of small pipes leads to one large pipe at the center of the pool, and extrudes a continuous stream of brownish-black tailings water.

Baosteel Rare Earth Research Institute Director Ma Pengqi said the resource value of the tailings pool is equivalent to the Bayan Obo iron ore mine in Baotou, the world’s largest rare earths deposit with approved reserves of 36 million tons, 36% of the world’s total.

In a study conducted by the company, researchers found that the proportion of rare earths in the 180 million tons of slag was higher than the total estimated reserves of raw ore in Bayan Obo. The average grade of rare earths is much more concentrated at 7% in the tailings, compared to 5.5% in raw ore.

Ma has conducted research on the pool for decades and estimates that the total commercial value of the tailings pond is over 1 trillion yuan, with 500 billion from rare earths and over 600 billion in other mineral deposits.

Many scholars point out that the Baosteel tailings pool was the result of inefficient mining practices, and the by-product created will make further mineral extraction more difficult.

When Baosteel was established in the 1950s, the steel mill and ore processing plant had to be put 100 kilometers away from the Bayan Obo mining site on the outskirts of Baotou near the Yellow River as the mining site lacked water resources. The mine dump was built near the steel mill.