Major partner won't expand stake in mine near Ely

A big Chilean mining company has decided not to increase its ownership stake in a firm exploring northern Minnesota for what could be the world's largest untapped source of copper and other precious metals.

Antofagasta could have assumed majority ownership of Twin Metals Minnesota. But Antofagasta officials said that while the venture has "long term geological attractions," the company's focus is on "prioritizing projects with the highest value and lowest risks."

The firm's partner in the Minnesota mining project, Toronto-based Duluth Metals, now has the option to buy out Antofagasta for $230 million.

"We would have to organize that funding in order to execute the buy-back," said Christopher Dundas, executive chairman of Duluth Metals. "Currently we do not have the money in treasury in order to execute the buy-back."

If Duluth Metals declines to buy out Antofagasta, the company must pay off a $10 million loan with cash or stock.

The Duluth Metals stock price has dropped by about 60 percent in the past year to under $1.