Anglo American posted an annual loss of $3.1 billion on Thursday after taking an impairment of $3.8 billion, mostly due to its ailing diamond unit, as it races to restructure into a major copper producer following a bruising takeover battle with BHP last year.

Anglo is considering either selling or listing De Beers, the carrying value of which is now about $4bn. That includes about $2bn worth of stock, a similar amount to last year.

Anglo American (OTCQX:AAUKF) (OTCQX:NGLOY) said Thursday it wrote down the value of its struggling De Beers diamond business by another $2.9B, after already writing down the business by $1.6B to $7.6B last year.