What is sulfide mining?

“Sulfide mining” is a term used in the Upper Midwest to refer to mining metals that are found in sulfide-bearing rock.

It also known by two other names:

  1. “Non-ferrous mining,” (which simply means “not iron mining”), a term used often by state agencies and the legislature; and
  2. “Hardrock mining,” a term used by much of the rest of the country which refers broadly to mining hard minerals such as gold, silver, iron, copper, zinc, nickel, and lead, in contrast to softer minerals such as coal or tar sands.

Sulfide mining is simply a form of hardrock mining that does not include iron mining.

In sulfide mining, it is the metals found within sulfide ores that are sought. In Minnesota, the sulfide mining proposals and exploration activities to date are focused primarily on extracting copper, nickel, platinum, palladium and gold, which make up only a very small fraction of the ore.

These metals have many functions in modern society. Copper is used in electrical systems, automotive components, and in new wind turbines. Nickel is used to make stainless steel and hybrid car batteries. Platinum, palladium and gold are used for making catalytic converters, fuel cells, medicine, and jewelry. Laptop computers and cell phones contain many of these metals.

Mining metals in sulfide ores can be done in two ways: in underground mines when the ore deposits are very deep, and in open-pit mines when the deposits are relatively shallow.

  • Underground mines involve the excavation of deep shafts, while open-pit mines are created by scraping off the surface soils and rocks, and digging crater-sized holes to reach the ore.
  • Mining companies often favor open-pit mines as they are less expensive to design and operate, but they also disturb a much larger amount of the surface. In the United States, 97 percent of all metals are now mined in open pits (PDF). Once the metals of interest are chemically extracted form the mined rock, large volumes of wasterock need to be disposed of.