Manganese is a strategic and critical metal used in alloys, mainly stainless steel. Other uses of manganese include production of dry cell batteries, in plant fertilizers and animal feed, and as a brick colorant. Currently, the U.S. imports 100% of the manganese we use, mostly from Gabon, Australia, and South Africa. There has been no manganese mining in the U.S. since 1970. The USGS estimates the value of imported manganese ore and compounds to be $1.4 billion in 2012.
That may change if Wildcat Silver’s Hermosa project comes on line. The project is located 50 miles south of Tucson near the town of Patagonia. The project, in final exploration stage, is being developed for silver, but it contains a considerable manganese resource also. Wildcat’s preliminary economic assessment estimates a measured and indicated resource of 236 million ounces of silver and an inferred silver resource of an additional 79 million ounces. Wildcat estimates that annual production will be 4.1 million ounces of silver, 233,000 tons of manganese carbonate, 20,187 tons of zinc cathode, and 960 tons of copper. Project life is estimated at 16 years. The company is researching the most economical way to extract the manganese. You can see some nice cross-sections of the mineralized zones here. The sections show intercepts of mineralization and average metal grades.
The project is, of course, receiving heavy opposition from environmentalists who seem to want no mining of anything anywhere.
Numerous manganese deposits are scattered over a large region in western Arizona and extend into southeastern California. These deposits are low grade (generally only a few percent Mn) and formed during the past 25 million years. Most historic production occurred between 1953 and 1955 when the US Government purchased manganese at above-market prices. Total historic production is ~100,000 metric tons of manganese (226 million lbs.) from 24 mining districts.
The Aguila manganese mineral district, with 42 million pounds of historic manganese production, is within the proposed Sonoran Desert Heritage National Conservation Area in the northern Big Horn Mountains west of Phoenix. The Black Dome district, with 344 thousand pounds of historic manganese production, is located north of the Hieroglyphic proposed Special Management Area. Manganese in these districts has not been in economic concentrations historically, but could become so if serious supply disruptions occur and/or prices increase sufficiently. However, if the Sonoran Desert Heritage Area is formally established, these resources will be off limits unless the proposed areas are excluded.
The Arizona Geological Survey has a special report on the mineral potential of the proposed heritage area (download full report here, 25Mb). The proposed heritage area encompasses almost one million acres.
Wildcat’s Hermosa project will have to navigate the byzantine bureaucratic maze of the National Environmental Policy Act (see: How NEPA crushes productivity), but if it does so successfully, it will become the only manganese producer in the United States.