Toronto-based Hudbay Minerals Inc. has identified an additional 591 million tons of copper-bearing rock in deposits adjacent to its proposed mile-wide, half-mile deep Rosemont open pit copper mine that it says could be economically mined in the future.
The additional resources were disclosed in a March 31 feasibility study required by Canadian regulators and used to obtain financing for the project. The disclosure of additional resources equal to what the company already plans to extract from the pit mine raises questions about the scope and lifespan of the project and resulting adverse impacts.
The currently proposed Rosemont pit is located within a larger area the technical report defines as the “resource pit shell.” The resource pit shell extends over the Santa Rita’s ridgeline and down the western slope. The additional 591 million tons of mineralized rock lies outside the Rosemont pit but within the resource pit shell.
The Rosemont mine would be constructed on the northeastern flank of the Santa Rita Mountains on the Coronado National Forest southeast of Tucson. The mining would generate 1.25 billion tons of waste rock and mine tailings. Hudbay intends to dump the waste into 700-foot high “earthforms” spread across 3,000 acres of national forest.
The feasibility study also raises the estimated cost of constructing the mine complex to $1.9 billion, up 21 percent from the company’s $1.5 billion projection made in Feb. 2015. Augusta Resource, the previous owner of the Rosemont site, estimated the mine would cost $1.2 billion in 2012 and $890 million in 2009.
Hudbay’s current plans call for mining 592 million tons of ore from the open pit that would contain 5.3 billion pounds of copper, 142 million pounds of molybdenum and 79 million ounces of silver. The company states it plans to process 90,000 tons of ore per day and produce an average of 279 million pounds of copper per year over the estimated 19-year life of the pit. Continue reading