Growing Strong Industries ~ Developing New Ideas ~ Nurturing Natural Resources

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Helen Lucas
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2 Sulfide Mining is a commonly used term to describe mining operations that mine metallic sulfide ore minerals Sulfide Mining is actually a misnomer the main objective of mining is generally not the sulfur, but the metallic element that is chemically bonded with the sulfur Common sulfide ore minerals can include the following: Chalcopyrite (CuFeS 2 ) an ore of copper Cubanite (CuFe 2 S 3 ) an ore of copper Pentlandite ((Ni,Fe) 9 S 8 ) an ore of nickel Millerite (NiS) an ore of nickel Talnakhite(Cu 9 (Fe,Ni) 8 S 16 ) an ore of copper/nickel Sulfide minerals can also be gangue (waste) minerals: Pyrite (FeS 2 ) fools gold Pyrrhotite ((Fe,Ni,Co,Cu) 1 x S) may be used as Ni ore

3 Aggregates (silicates, carbonates) Statewide, surficial glacial deposits and crushed stone Open Pit mining Clays (silicates) Minnesota River Valley Open Pit mining Silica Sands / other Sandstone Products (silicates) SE and SC MN Open Pit and Underground mining Ornamental Stone (silicates) SW Minnesota, Central Minnesota, NE Minnesota Open Pit mining Manganese (oxides) North Central MN (60 mines) Underground and Open Pit mining Iron Ore (oxides) Northeastern MN more than 360 mines over the past 130 years Underground and Open Pit mining

4 General Area of Cu Ni PGM Mineralization Late Intrusions Layered Series Hosts Cu Ni PGM Deposits Volcanic Rocks Near Minnesota s North Shore

5 North America tried to split apart ~1.1 billion years ago in what is called the Mid-Continent Rift. The enormous amount of heat combined with an incredible volume of magma mobilized large amounts of metals from deep in the earth up into the crust. These metals precipitated as sulfide minerals in the Duluth Complex.

6 NorthMet Deposit (PolyMet Mining) Mesaba Deposit (Teck American Inc.) Birch Lake Deposit (Twin Metals Minnesota) Maturi,Deposit (Twin Metals Minnesota) PolyMet SDEIS Proposed Action 533 million tons of ore and waste rock to be mined (32,000 tons/day) 225 million tons ore 308 million tons waste rock (after Severson et al., 2013; SDEIS, NorthMet Mining Project and Land Exchange, 2013) (Hudak and Peterson, 2014) Growing Strong Industries ~ Developing New Ideas ~ Nurturing Natural Resources

7 Relative to Magmatic Cu-Ni- PGM Deposits Worldwide # 3 in contained Nickel # 1 in contained Copper # 4 in contained PGE Current Duluth Complex overall resource (0.1% Cu equivalent) is as great as 7 billion tons with average grades running 0.66% Cu and 0.2% Ni (Miller and Nicholson, 2013) (after Eckstrand and Hulbert, 2007; Jones et al., 2014; Peterson, 2010; and Miller, 2011)

8 (Hudak and Peterson, 2014)

9 Similarities 1. All deposits located near the basal contact of the 1.1 b.y. old Duluth Complex; 2. All are composed of Cu Ni ±Co sulfide minerals and PGMs + Au ±Ag; and 3. PolyMet and Twin Metals have Platinum Group Metals + Gold ± Silver that add value to the deposit. Mesaba also has PGMs. Differences 1. To date, only PolyMet has submitted a revised Environmental Impact Statement (EIS) plan and is currently preparing their Final Environmental Impact Statement. Based on the SDEIS, PolyMet plans to mine their deposit via open pit mining methods; 2. Twin Metals plans an underground mining operation based on highlights of their prefeasibility study (available at metals.com/twinmetals minnesota project offers extraordinary economic opportunity); 3. Twin Metals and Mesaba are still drilling, collecting environmental data, and developing final mining, processing, and environmental plans and have not submitted their EIS to the State for review and comment; 4. Very limited drilling and geological investigations are ongoing by smaller companies (e.g., Encampment Resources Serpentine Deposit).

10 Steven A. Hauck George Hudak

Jim Miller Department of Geological Sciences Precambrian Research Center University of Minnesota Duluth

Future of Base and Precious Metal Mining in Minnesota Jim Miller Department of Geological Sciences Precambrian Research Center University of Minnesota Duluth A Looming Stewardship Question for Minnesotans: