Mining giant BHP Billiton's spin off South32 Wednesday flagged pre-tax impairments of $1.9 billion on manganese and coal assets in Australia and South Africa as commodity prices struggle. South32 - which debuted on the Australian Securities Exchange in mid-May - demerged from the Anglo-Australian giant and has a diversified metals and mining portfolio, including aluminum, coal, nickel, manganese, silver, lead and zinc, with most of its mines in the southern hemisphere. The charges of $1.9 billion stem from $445 million at the Australian Manganese unit, $882 million at South Africa Manganese and $539 million at the Wolvekrans Middelburg complex within South Africa Energy Coal, South32 said in a statement to the Australian stock exchange. They largely offset the previous fair value uplift of $2.1 billion for its manganese assets, the Perth-headquartered company said.