Peabody Energy Corp. will permanently close its Air Quality Mine in Vincennes, Indiana, because of “soft” conditions that make operations uneconomic.

Peabody expects to incur a one-time charge of $75 million in the third quarter related to the writedown of assets, according to a statement today.

The mine produced 1.2 million tons of low sulfur coal in 2011, according to the statement. The mine supplies power plants and industrial customers in Indiana and Illinois, according to the company’s website.