"If the US Fed steps into buy bonds and keep real yields negative tonight, then you might see a short-covering rally in tech. If not, tech will continue to slide."
Meanwhile, AGL Energy hit record low after its chief executive officer resigned just less than a month after the power producer announced its plans to split its businesses into two.
That demonstration plant will run for the rest of the year as Rio decides whether to spend $50 million to build a full-scale production plant with annual capacity of 5,000 tonnes.
Rio has produced borates - a group of minerals used to make soaps, cosmetics and other consumer goods - for nearly a century in the Mojave Desert, about 120 miles (195 km) north of Los Angeles.
The European Commission, which oversees trade policy for the 27-nation European Union, has set anti-dumping duties of between 21.2% and 31.2% on Chinese producers of aluminium extrusions in the form of bars, rods, profiles or tubes.
The tariffs are lower than the provisional duties of 30.4% to 48.0% imposed midway through the investigation.
Rio operates the mine via its Canadian subsidiary Turquoise Hill, which owns 66% of Oyu Tolgoi. The rest of the mine has been owned by the Mongolian government since the project was launched in 2009.
Activist investor Pentwater Capital Management LP is Turquoise Hill's largest shareholder after Rio with a 9% stake.