CRITICALITY CONCEPTS DOMINIQUE GUYONNET BRGM Course objectives Clarify

CRITICALITY CONCEPTS DOMINIQUE GUYONNET BRGM

Course objectives • Clarify the concepts underlying criticality assessments • Provide an overview of methodologies • Emphasize possibilities and limitations • Illustrate with reference to specific critical raw materials © BRGM, 2019 2

Contents 1. Introduction: the increasing use of mineral raw materials 2. Factors influencing criticality 3. Overview of some criticality assessment methodologies 4. “Critical” about criticality 5. Conclusions © BRGM, 2019 3

1. Introduction : the increasing use of mineral raw materials • Main mineral raw materials consumed by a European in Kg/yr © BRGM, 2019 4

1. Introduction : the increasing use of mineral raw materials • Population growth? Evolution of population since the Neolithic revolution (in billion inhabitants) Projections (Source : United Nations, 2015) © BRGM, 2019 5

1. Introduction : the increasing use of mineral raw materials • Mineral raw material consumption growing much faster than global population Source : JF Labbé, BRGM © BRGM, 2019 6

1. Introduction : the increasing use of mineral raw materials • Rather: population growth + emergence of consuming class Source : Mc. Kinsey and BRGM; World Materials Forum, June 2016 © BRGM, 2019 7

1. Introduction : the increasing use of mineral raw materials • Material consumption - example of Aluminium: how much additional Al production required to satisfy the 3 billion additional members of the consuming class between 2010 and 2030 (Brookings Institute)? • If 3 billion people go from 1 kg Al/yr to 25 kg Al/yr, we need 72 Mt Al/yr extra (for reference: world Al production in 2017 was 60 Mt) Source : USGS, 2010 © BRGM, 2019 8

1. Introduction : the increasing use of mineral raw materials Historical evolution of yearly primary aluminium production until 2015 and extrapolation over next 40 years • Simulationofofconsumption Simulation sameincreaserateofof atatsame 4, 7%per peryear 4, 7% Need to account for increase of world demand by 2030 Best-fit of of consumption Best-fit consumption increase rate: 4, 7% perper year increase rate: 4, 7% year Cumulated production since origin to 2015 : 1, 22 Gt Al Additional cumulated production required from 2016 to 2030 to maintain a 4, 7% growth rate : 1, 24 Gt Al © BRGM, 2019 9

1. Introduction : the increasing use of mineral raw materials • Reminder of the significance of exponential growth: growth rate versus doubling period © BRGM, 2019 10

1. Introduction : the increasing use of mineral raw materials • Driver: Chinese metal consumption (923 Mt in 2018) Example of steel. Between 2001 and 2015: 12, 7% annual growth! Source : Ph. Russo, Arcelormittal © BRGM, 2019 11

1. Introduction : the increasing use of mineral raw materials Source : Reuter, M. et al. • Another essential driver: diversification of elements in products © BRGM, 2019 12

1. Introduction : the increasing use of mineral raw materials • MRMs for the energy sector © BRGM, 2019 13

2. Factors influencing criticality • The term « Mineral Criticality » starts to appear in the years 2000 in US documents; e. g. : National Research Council report 2007 « Minerals, Critical Minerals and the U. S. Economy » : • In the latter, criticality assessment is performed in a 2 dimensional matrix: ü Supply risk ü Impact of Supply Restriction • A mineral is considered « critical » if it scores high in this matrix in a relative sense: mineral A is considered more critical than mineral B • Most methods adopt a 2 -D matrix © BRGM, 2019 14

• EU method tends to be dichotomous: a MRM is either « critical » or « noncritical » , according to a threshold Supply risk 2. Factors influencing criticality Non-critical MRM Critical MRM High supply risk, low economic importance High supply risk, high economic importance Non-critical MRM Low supply risk, low economic importance Low supply risk, high economic importance Economic importance • Some authors argue that criticality is not binary (a), but rather a question of degree (b) (Graedel, Gunn & Tercero-Espinoza, 2014) Source : Critical Metals Handbook © BRGM, 2019 15

2. Factors influencing criticality 5 th Avenue, NYC, April 15 th 1900 • Time factor Spot the car in 1900 Source: Tony Seba, US National Archives. In R. Friedland, World Materials Forum, 2017 © BRGM, 2019 16

2. Factors influencing criticality 5 th Avenue, NYC, March 23 rd Spot the horse in 1913 © BRGM, 2019 17

2. Factors influencing criticality • Scale factor – criticality differs at different scales e. g. An industry A country A continent The world © BRGM, 2019 18

2. Factors influencing criticality • Geopolitical factor - risk of supply disruption ü e. g. CN-JP territorial dispute over Senkaku islands ü In 2010 CN enforced stricter export quotas on REEs and blocked exports to JP © BRGM, 2019 19

2. Factors influencing criticality Intense speculation on REE prices Prices of some rare earths, metal 99%, in US$/kg FOB China Source: JF Labbé, BRGM © BRGM, 2019 20

2. Factors influencing criticality Cost of Dysprosium, metal 99%, in US$/kg FOB China 3 410 $/kg on July 14 th 2011 6 tor ac af n a by 13 M ul tip tio a lic by c fa ion vis Di to 0 r 1 257, 5 $/kg on July 28 th 2016 32, 1 $/kg on average in 2002 -2003 © BRGM, 2019 21

2. Factors influencing criticality • 24 Mt @ 7, 8% REO 1, 87 Mt REO Attempts to escape from the Chinese monopoly: ü Mountain Pass (USA) ; company Molycorp reopened in 2012 after prolonged inactivity. Went bankrupt because of low prices and closed in 2015. Mining has resumed since Jan 2018. ü Mount Weld (Australia) ; Company LYNAS. Survived thanks to « offtake » contracts. Source : J. Tuduri © BRGM, 2019 22

2. Factors influencing criticality MOLYCORP stock LYNAS stock © BRGM, 2019 23

• © Brgm, G. Lefebvre; D. Guyonnet Rare Earths Tungste n Mercur y Graphit e Fluorit Antimon e y Arseni c Magnesit e Bismut h Coking coal Phosphat e Vanadiu m Steaming coal Lead Molybdenu m Ti n. Zinc Barit e Talcu Gypsum/anhydri m te Iron ore Bauxit e Titanium dioxide Sulfu r Gol Lithiu d m Manganes e Silve r. Potas h Zirconiu m Coppe r Berylliu m Cobal t Nicke Tantalu l m Boron Uraniu m. Chromit e. Niobiu m. Platinu m Palladiu m Rhodiu m Magnesium Galliu metal m Refined Germaniu cobalt m Silico n Primary iron Aluminiu m Alumina Steel Indiu m Cadmiu m Refined copper Ferrochro me Seleniu m Nickel metal Rheniu melluriu T m 2. Factors influencing criticality Production Concentration factor China’s share in the global production of some mineral raw materials (2015 data) Mine production Refining / Metallurgy Source : JF Labbé, BRGM China produces > 2/3 of world production (domination/monopoly). Net exporter. China produces 1/3 - 2/3 of world production. Importer or exporter. China produces < 1/3 of world production. Net importer. © BRGM, 2019 24

2. Factors influencing criticality ü An indicator of market concentration: the Herfindahl-Hirshman index: where si is country « i » ’s share in world production and « n » is the number of country’s producing the raw material. ü So if 2 countries have an equal share of the market: HHI = 0, 52 + 0, 52 = 0, 25 + 0, 25 = 0, 5 ü HHI varies between 1/n (equal shares between n countries) and 1 (total concentration in one country). ü Often the actual percent values (eg. 5 for 5%) are used and then HHI varies between 10 000/n and 10 000 © BRGM, 2019 25

2. Factors influencing criticality Ranking (used in finance) : ü HHI < 0, 01 (or 100): Highly competitive market (very well distributed production) ü 0, 01 (or 100) < HHI < 0, 15 (or 1 500): Unconcentrated production ü 0, 15 (or 1 500) < HHI < 0, 25 (or 2 500): Moderate concentration ü HHI > 0, 25 (or 2 500): High concentration Proposal: ü HHI > 0, 5 (or 5 000): Very high concentration (monopoly) © BRGM, 2019 26

2. Factors influencing criticality • Good Governance o A country with poor governance is less reliable in terms of supply than a country with good governance o The World Governance Index (WGI) is an indicator developed in 2008 by the Forum for a new World Governance (Fn. WG) o It aims to provide, each year, an image of the situation of world governance o The index is based on serveral indicators. One of these indicators (political stability) is used in a criticality calculation methodology (Yale methodology; see below) © BRGM, 2019 27

2. Factors influencing criticality • Geological availability factor Basis of calculation : Reserve Base (tons) _________ A source of misunderstanding among the general public Production (tons/yr) New Scientist, 2007 © BRGM, 2019 28

2. Factors influencing criticality • Part of the misunderstanding comes from the confusion between resources and reserves • Some definitions (based on JORC; Joint Ore Reserves Committee, 2012) : ü Mineral resources are concentrations or mineralizations of natural substances present in the earth’s crust (to form a deposit) which present certain characteristics of quantity, quality, etc. , such that there are reasonable prospects for economic extraction of these substances ü Ore reserves are a portion of mineral resources for which it has been proven that it is economically, technically and legally feasible to extract the ore Note: there was a major effort in terms of classification in the aftermath of the Bre-X scandal (Busang, Indonesia, 1997) © BRGM, 2019 29

2. Factors influencing criticality • General relationship between exploration results, mineral resources and ore reserves (JORC, 2012) Reserve Base (resources from which reserves are defined) © BRGM, 2019 30

2. Factors influencing criticality Resources / Reserves schematic © BRGM, 2019 31

2. Factors influencing criticality • • Relationship between tonnage and cutoff grade As metal price increases, cutoff grade decreases and so ore reserves (tonnage) increase (what was not economic becomes economic) Price goes down, Cutoff goes up Price goes up, Cutoff goes down © BRGM, 2019 32

2. Factors influencing criticality “ Estimating what’s left to extract based on the “Reserve Base” is analogous to estimating what you have left to eat based on what’s left in your refrigerator ” (source: a mining geologist) © BRGM, 2019 33

2. Factors influencing criticality Comments on the « mineral resource depletion » issue • The « peak metal » / « fixed stock » approach is not valid: the reserve base is changing all the time. • The issue is much less « Mineral resource depletion » than « access to mineral resources » • This access is constrained by many factors (production concentration, geopolitical risks, environmental constraints, social acceptability, aversion to financial risk of investment banks, …) • While there may still be ore to mine out there, it is becoming increasingly difficult to mine due to decreasing ore grades (need more energy to get the stuff out) • Although in the short to medium term, primary resources will continue to be the main source of mineral raw materials, recycling, reuse, substitution, etc. must be developed, to reduce waste flows and offset emissions related to primary resource extraction • Recycling can help offset depletion, but not if we continue increasing consumption at such rates © BRGM, 2019 34

2. Factors influencing criticality • Objective: resource efficiency. Reduce mineral raw material consumption per service while reducing environmental impacts (environmental rucksack) water, rock, energy, chemicals, land area, biodiversity, risks, … (+ economic & social…) © BRGM, 2019 35

2. Factors influencing criticality • Ore grade factor Declining ore grades: gold (Mudd, 2009) © BRGM, 2019 36

2. Factors influencing criticality Same for copper © BRGM, 2019 37

2. Factors influencing criticality • Environmental factor Mine waste production in Australia Source: Gavin Mudd © BRGM, 2019 38

2. Factors influencing criticality Source : National Geographic © BRGM, 2019 39

2. Factors influencing criticality • Social factor © BRGM, 2019 40

2. Factors influencing criticality • Industry structure factor - the « metal wheel » (M. Reuter et al. ) Importance of base metallurgy for recovery of smaller metals (and for recycling) © BRGM, 2019 41

2. Factors influencing criticality • must keep in mind the value chain Source : UNEP, 2011 Prod © BRGM, 2019 42

2. Factors influencing criticality In summary • • Criticality assessment is a form of Risk Assessment • Risk assessment traditionally consists in evaluating two components of risk: • There are quantitative and qualitative risk assessments (see for ex. the European methodology for • Criticality assessments are somewhere in-between (semi-quantitative risk assessments) Risk is the potential for losing something of value. In the case of CRMs, the value can be: ü economic wealth, ü job loss, ü deterioration of social fabric, infrastructure, know-how, ü energy management, … ü the magnitude of the loss ü probability that the loss will occur contaminated soil risk assessments) © BRGM, 2019 43

3. Overview of some methodologies • Yale methodology ü Geographical focus: United States (corporate, national and global levels) ü Extension of the U. S. National Research Council studies started in 2006 ü Definitions of criticality according to 3 dimensions (Graedel et al. , 2011): o o o Supply risk Vulnerability to Supply Restriction Environmental implications ü Progressive approach to define a “degree” of criticality of the MRM ü Criticality Assessment: a score is attributed to several indicators resulting in a position in a 3 -D criticality space © BRGM, 2019 44

3. Overview of some methodologies ü Various indicators are related to each one of the 3 dimensions Graedel et al. , 2015 © BRGM, 2019 45

3. Overview of some methodologies • Criticality Assessment results depend on the choice of indicators • For Supply Risk, distinction is made between Medium Term and Long Term indicators • Each indicator is associated with measurable technical concepts: reserve base, companion metal fraction… • By default, equal weights are assigned to all indicators © BRGM, 2019 46

3. Overview of some methodologies • Methodology intended to allow flexibility among potential users and different organizational levels (corporate, national, global) • Examples published in the Journal of Industrial Ecology: ü REEs ü Zinc, Tin, and Lead Family elements ü Seven specialty metals (Ba, Bi, Hg, Sc, Sr, Sb, Tl) Nassar et al. , 2015 Harper et al. , 2015 Panousi et al. , 2016 © BRGM, 2019 47

3. Overview of some methodologies • EU methodology ü Geographical focus: European Union ü 3 Criticality Assessment studies to-date: 2010, 2014, 2017 ü Definitions of criticality according to 2 dimensions o o Economic importance to the EU (EI) Vulnerability to supply disruption (Supply Risk; SR) ü Dichotomous approach : a raw material is either « critical » or « non-critical » , according to a threshold defined by the Joint Research Center (JRC) ü A criticality score is calculated for each Raw Material using the same parameters and equations © BRGM, 2019 48

3. Overview of some methodologies • 2017 methodology revision was motivated by the need to: üBetter capture risks of trade distortion such as: o Export taxes o Physical quotas o Export prohibitions üAddress more adequately the entire value chain (identify bottlenecks in the steps of extraction or metallurgy, shifts in supply concentration, etc. ) üDifferentiate Global supply and European supply üBetter account for supply from secondary sources and for substitution potentials üHave a more transparent allocation of raw material uses to NACE sectors © BRGM, 2019 49

3. Overview of some methodologies • In 2017, the measure of Economic Importance (EI) was calculated from: Where: As = share of metal demand in application “s” relative to total demand Qs = Gross Value Added (GVA) of 2 -digit NACE sector allocated to application “s” Qmax = Largest GVA of all 2 -digit NACE sectors (scaling factor) • SIEI = Substitutability Index related to Economic Importance Supply Risk (SR) was calculated from: Where: (HHIWGI-t )GS= Herfindahl-Hirschmann Index for Global Supply, taking into account World Governance Index score and a trade factor (t) (HHIWGI-t )EU 28 = Herfindahl-Hirschmann Index for EU 28 Supply, taking into account World Governance Index score and a trade factor IR = Import Reliance (%) Eo. LRIR = End of Life recycling input rate SISR = Substitutability Index related to Supply Risk © BRGM, 2019 50

3. Overview of some methodologies EU CRM list 2010 © BRGM, 2019 51

3. Overview of some methodologies EU CRM list 2014 © BRGM, 2019 52

3. Overview of some methodologies EU CRM list 2017 © BRGM, 2019 53

3. Overview of some methodologies Question: why does Scandium have more Economic Importance than Lithium? © BRGM, 2019 54

3. Overview of some methodologies • According to USGS, the global supply and consumption of Sc is around 10 -15 tons per year. • Scandium uses in 2016: ü The main uses were in Al-Sc alloys and in solid oxide fuel cells (SOFC) ü Al-Sc alloys are produced for sporting goods (luxury golf clubs) ü Al-Sc alloys are considered a potential substitute for Titanium (expensive) in e. g. aircrafts. But this is currently at R&D stage and no aircraft industry would suffer from Sc-supply disruption ü Sc is used in small quantities in a number of electronic applications ü Other minor uses: ceramics, lasers, lighting, … • So Scandium is a niche market See hands-on exercise… © BRGM, 2019 55

3. Overview of some methodologies • Some advantages of the EU Criticality assessment methodology ü Important communication tool for policy makers and (some) industrial companies ü Transparency of the methodology and sources of data ü Snapshot of the parameters affecting criticality of each specific Raw Material (at the time of the study), described in the additional Factsheets. • Some drawbacks of the EU Criticality assessment methodology ü Complexity of the formulas and constraints imposed by transparency (e. g. use of public data only) are not always compatible with the complexity of the markets at stake ü Some parameters affecting criticality are omitted (see hands-on exercise) © BRGM, 2019 56

3. Overview of some methodologies • BRGM methodology ü Geographical focus: France ü Criticality Assessment studies : About 20 CRM covered from 2010 to 2017, according to French governments’ requests and priorities ü Definitions of criticality according to 2 dimensions : o o Strategic importance for the French industry (y-axis) Supply risks (x-axis) ü Progressive approach : o o Not one but several thresholds to define the degree of exposure to the risks No calculation but rather an indicative position based on several parameters and expert judgement ü The objective is to give criticality indicators to policy makers and industry, as well as recommendations of actions to carry out © BRGM, 2019 57

3. Overview of some methodologies Area of very high criticality. Conservative actions should be taken at national level. Close monitoring of criticality indicators required Area of high criticality. Active monitoring recommended (monitoring of markets, alerts, proposals for remedial action) Area of average criticality. Specialized monitoring recommended (regular update of criticality assesssment) REE Rare Earth Elements Group PGM Platinum-Group Metals Source : BRGM, 2017 © BRGM, 2019 58

3. Overview of some methodologies ü Criticality assessments follow a detailed list of indicators : o Evolution of use and consumption o Evolution of world production and known resources / reserves o Substitution o Recycling o Prices o Restrictions to international trade, regulations o French production and resources o French industrial sector o External trade and French consumption o Other © BRGM, 2019 59

3. Overview of some methodologies One of the hardest metals Example: Tungsten • World uses of Tungsten in 2015 Source: Argus/ITIA Hardness (Mohr scale) • Distribution of tungsten uses by industrial sector: Source : BRGM, Mineralinfo. fr © BRGM, 2019 60

3. Overview of some methodologies • Historical trends Mine production by country Production average annual growth rate : • 2010 - 2015 : 2% • 1996 - 2015: 5% • 1915 - 2016: 2, 82% Evolution of prices Source : BRGM, Mineralinfo. fr © BRGM, 2019 61

3. Overview of some methodologies • Tungsten current production and reserves Distribution of known world reserves in 2016 World mine production in 2015 Source : WMD 2017 World total: 88, 75 kt W World total: 3, 14 Mt W Source : USGS 2017 ü 3 Mt reserves are equivalent to 35 years of production at the 2015 level (88 kt W). ü With a 2% production annual growth rate (as observed since 2010), these reserves would be depleted in 26 years © BRGM, 2019 62

3. Overview of some methodologies • W: synthesis of criticality factors Source : BRGM, Mineralinfo. fr © BRGM, 2019 63

3. Overview of some methodologies Conclusion: very high criticality of Tungsten (W) at the French level due in particular to: ü The wide variety of uses in industry (e. g. Tungsten carbide tools) ü The strong dominance of China over the global market Strategic importance for French industry • Source : BRGM, Mineralinfo. fr Supply Risk © BRGM, 2019 64

4. Critical about criticality • Several critical appraisals of criticality assessment methodologies in the literature. For example : • • This paper advocates a more “quantitative” approach to risk in criticality assessments. Difficulty: due to abovementioned diversity/complexity of risk factors, it is difficult to build a comprehensive quantitative “model” of factor interactions © BRGM, 2019 65

4. Critical about criticality • Criticality is a dynamic, ever-changing characteristic of a MRM. Therefore assessments need to be periodically updated • Regarding methodologies, we feel there should be more scope for feedback from industry/expert stakeholders before issuing CRM assessment results • Before performing a criticality assessment, key questions are : ü ü Critical for who? Criticality for what? (decision-making) • Past experience has shown benefits of criticality analyses especially at a corporate level. In particular when analyses have led to actions in terms of reducing company exposure to problematic elements • Scope for a harmonized methodology? . . . • Addressing uncertainties? . . . © BRGM, 2019 66

4. Critical about criticality • Other example: Buijs et al. (see references). These authors identify the following limitations in the critical minerals approach: ü Bias towards technology minerals by emphasizing (a) high-tech applications and (b) the role of market power of producers in small markets, ü Lack of predictive power beyond the short term, ü Failure to distinguish between short-term and long-term problems, ü Tendency to overstate the economic impact of a possible supply disruption of ‘critical’ minerals, ü Exaggerated focus on risks related to the mining and export of raw materials, but not on the larger production chain (e. g. refining, transport, and trade in semi-products). • According to the authors, most of the minerals that historically have been classified as “critical”, have in fact never caused significant problems (e. g. PGMs). • An issue specific to the EC method will be addressed during the “hands-on” session © BRGM, 2019 67

4. Critical about criticality • Example of CRM list for specific applications: © BRGM, 2019 68

4. Critical about criticality Illustrates importance of time factor: in 2013, Eu, Tb were considered highly critical Source : JRC, 2013 © BRGM, 2019 69

4. Critical about criticality • But: fluorescent lighting has been rapidly superseded by LEDs Overseas market demand in million units 1. 271 1. 282 27 1. 290 0 1. 293 9 213 344 1. 291 8 307 1. 286 8 269 1. 279 7 1. 268 230 7 190 1. 254 1. 237 10 1. 219 1. 199 9 9 150 110 271 360 460 216 -1 145 335 1. 226 -1 83 1. 195 37 113 1. 161 1. 127 57 8 91 -1 25 59 -4 36 133 161 638 602 645 527 200 570 604 591 320 1. 098 187 445 555 583 196 516 217 181 68 94 131 2015 2016 2017 189 248 308 360 407 2019 2020 164 163 Optimistic case 2021 2022 2023 264 169 450 24 2018 393 183 239 174 2012 - T 8 + T 12 Halo § 2016 LED market share = 20% - T 8 + T 12 mix § 2018 LED market share = 35% - T 5 Tri 2020 LED market share = 50% - LED engine § 1 Source: 1. 256 264 189 2013164 2014 284 1. 277 181 290 200 54 4 270 352 207 592 343 1. 288 221 381 199 609 42 394 186 547 21 7 167 596 152 11 1. 290 142 511 81 164 414 191 116 407 163 229 311 9 26 8 1. 287 211 271 2012 53 395 418 24 80 1. 281 1. 271 - T 8 + T 12 Tri - T-LED 20 44 42 2013 162 89 54 68 94 131 2014 2015 2016 2017 189 2018 248 2019 308 2020 360 2021 407 2022 450 2023 Pessimistic case § 2016 LED market share = 30% § 2018 LED market share = 60% § 2020 LED market share = 75% © BRGM, 2019 70

4. Critical about criticality • Phosphors containing Eu and Tb are now a very small share of the total market, which has much reduced their criticality Source: © BRGM, 2019 71

5. Conclusions • Restrictions to global supply of MRMs are more related to access to MRMs than to geological availability • Access is limited primarily by economic, geopolitical, environmental and social factors • Criticality assessments attempt to address the risk of supply disruption and economic/social damage through a multifactor ranking approach • These methods are screening tools. Attempts to be « precisely quantitative » are limited by the diversity and complexity of factors • Different methods deliver different results: there is no « correct » method; there is only adequacy of methods with specific user needs • Therefore values can only be compared for a given methodology and in a relative sense © BRGM, 2019 72

References for further reading ü Blengini, G. A. , et al. , 2017. EU methodology for critical raw material assessment : Policy needs and proposed solutions for incremental improvements. Resources Policy, 53, 12 -19. ü Buijs, B. , Sievers, H. , Tercero Espinoza, L. 2012. Limits to the critical raw materials approach. Proceedings of the Institution of Civil Engineers - Waste and Resource Management, 165(4), 201 -208. ü EC, 2017. Study on the review of the list of Critical Raw Materials. Final Report. European Commission. ü Frenzel et al. , 2017. Raw material ‘criticality” – sense or nonsense? Journal of Physics, D: Applied Physics, 50. ü Graedel, T. E. et al. , 2012. Methodology of metal criticality determination. Environmental Science & Technology, 46, 1063 -1070. ü Graedel, T. E. & Reck, B. K. , 2016. Six years of criticality assessments. What have we learned so far? Journal of Industrial Ecology, 20(4), 692 -699. ü NRC, 2008. Minerals, Critical minerals, and the U. S. Economy. Report of National Research Council. Washington, DC: The National Academies Press. © BRGM, 2019 73

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