Mining company BHP Billiton posted a 39-percent fall on the year in diamond output from the Ekati diamond mine in Canada's NorthWest Territories to 295,000 carats in the quarter that ended on December 31.
That compares with a figure of 481,000 carats in the year-earlier quarter, with production being "lower than all comparable periods", the company says in a statement.
Meanwhile, diamond production in the first half of its fiscal year dropped by 35 percent on the year-earlier period to 608,000 carats from 938,000 carats a year earlier.
BHP said it was selling its diamond business, including its 80-percent stake in the Ekati mine, to Harry Winston Diamond Corp for US$500 million.
"The transactions are subject to regulatory approval and other customary conditions. Completion is expected in the first half of calendar year 2013," the firm says.