Prices of the metal have been fallen in the second half of this year as the prospect of a rate rise, the first since 2006, would lift the opportunity cost of holding bullion.
About 3 million gallons of toxic wastewater, triple previous estimates, have poured from an old Colorado gold mine into local streams since Wednesday last week.
While the U.S. Environmental Protection Agency was investigating pollutants at an old gold mine, it accidentally released an estimated one million gallons of mining waste into a creek.