Graphite — Critical Mineral Resources of the US (PP 1802-J)

G.R. Robinson Jr., J.M. Hammarstrom & D.W. Olson · 2017 · Critical Minerals

Chapter J of PP 1802 — natural graphite resources globally. Covers flake, lump, and amorphous graphite types and their host environments (metamorphosed…

Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.

Graphite Chapter J of Critical Mineral Resources of the United States—Economic and Environmental Geology and Prospects for Future Supply Photograph of Graphite Professional Paper 1802-J U.S. Department of the Interior U.S. Geological Survey

Periodic Table of Elements Ta bl e El em en ts Modified from Los Alamos National Laboratory Chemistry Division; available at ://periodic.lanl.gov/images/periodictable.pdf. Cover.  Graphite. U.S. quarter for scale. Mineral collection of Brigham Young University Department of Geology, Provo, Utah. Photograph by Andrew Silver (BYU index 1-1023a).

Graphite By Gilpin R. Robinson, Jr., Jane M. Hammarstrom, and Donald W. Olson Chapter J of Critical Mineral Resources of the United States—Economic and Environmental Geology and Prospects for Future Supply Edited by Klaus J. Schulz, John H. DeYoung, Jr., Robert R. Seal II, and Dwight C. Bradley Professional Paper 1802-J U.S. Department of the Interior U.S. Geological Survey

U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S. Geological Survey William H. Werkheiser, Acting Director U.S. Geological Survey, Reston, Virginia: 2017 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit ://www.usgs.gov or call 1-888-ASK-USGS. For an overview of USGS information products, including maps, imagery, and publications, visit ://store.usgs.gov/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Robinson, G.R., Jr., Hammarstrom, J.M., and Olson, D.W., 2017, Graphite, chap. J of Schulz, K.J., DeYoung, J.H., Jr., Seal, R.R., II, and Bradley, D.C., eds., Critical mineral resources of the United States—Economic and environ­mental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, p. J1- J24, ://doi.org/ 10.3133/pp1802J. ISSN 2330-7102 (online)

Contents Abstract J1 Introduction J1 Commercial Classifications of Graphite J1 Natural Graphite J3 Synthetic Graphite J3 Uses and Applications J3 Demand and Availability of Supply J4 Graphite Prices and Pricing J4 Substitutes for Natural Graphite J4 Strategic and Critical Resource Issues J5 Geology J5 Geochemistry J5 Mineralogy J5 Deposit Types J6 Amorphous Graphite Deposits J6 Deposits of Flake Graphite Disseminated in Metasedimentary Rocks J7 Vein Deposits Containing Lump or Chip Graphite J15 Mining and Beneficiation Methods J16 Resources and Production J16 Distribution of Graphite Deposits and Districts J16 World Graphite Production and Resources J17 Exploration for New Deposits J19 Environmental Considerations J19 Mine Waste Characteristics J19 Human Health Concerns J20 Ecological Health Concerns J20 Carbon Footprint J21 Regulatory and Environmental Considerations J21 Problems and Future Research J21 References Cited J22

Figures

J1.  Diagram showing the arrangement of carbon atoms in graphite J6

J2.  World map showing locations of major graphite deposits and districts in the world, by commodity type J14

J3.  Plot of grade and tonnage for some of the amorphous and crystalline graphite deposits listed in table J3, by deposit type J16

J4.  Pie chart showing average annual natural graphite production for the period 2006-10, by country or region and amount J17 Tables

J1.  Characteristics of graphite commodities, deposits, and uses, by commodity type J2

J2.  Selected physical properties of graphite J3

J3.  Location, grade, tonnage and other data for selected graphite deposits and districts of the world J8

J4.  Estimates of world graphite resources, by country, commodity type, and resource category, in thousand metric tons of recoverable graphite J18

Conversion Factors International System of Units to Inch/Pound Multiply By To obtain Length angstrom (Å) (0.1 nanometer) microinch angstrom (Å) (0.1 nanometer) 0.000003937 mil micrometer (µm) [or micron] mil millimeter (mm) inch (in.) centimeter (cm) inch (in.) meter (m) foot (ft) meter (m) yard (yd) kilometer (km) mile (mi) Area hectare (ha) acre square kilometer (km2) acre square meter (m2) square foot (ft2) square centimeter (cm2) square inch (ft2) square kilometer (km2) square mile (mi2) Volume milliliter (mL) ounce, fluid (fl. oz) liter (L) ounce, fluid (fl. oz) liter (L) quart (qt) liter (L) gallon (gal) cubic meter (m3) gallon (gal) cubic centimeter (cm3) cubic inch (in3) cubic meter (m3) cubic yard (yd3) cubic kilometer (km3) cubic mile (mi3) Mass microgram (μg) 0.00000003527 ounce, avoirdupois (oz) milligram (mg) 0.00003527 ounce, avoirdupois (oz) gram (g) ounce, avoirdupois (oz) gram (g) 0.03215075 ounce, troy kilogram (kg) ounce, troy kilogram (kg) pound avoirdupois (lb) ton, metric (t) ton, short [2,000 lb] ton, metric (t) ton, long [2,240 lb] Deposit grade gram per metric ton (g/t) 0.0291667 ounce per short ton (2,000 lb) (oz/T) Pressure megapascal (MPa) bar gigapascal (GPa) 10,000 bar Density gram per cubic centimeter (g/cm3) pound per cubic foot (lb/ft3) milligram per cubic meter (mg/m3) 0.00000006243 pound per cubic foot (lb/ft3) Energy joule (J) 0.0000002 kilowatthour (kWh) joule (J) 6.241 × 1018 electronvolt (eV) joule (J) calorie (cal) kilojoule (kJ) 0.0002388 kilocalorie (kcal)

International System of Units to Inch/Pound—Continued Multiply By To obtain Radioactivity becquerel (Bq) 0.00002703 microcurie (μCi) kilobecquerel (kBq) microcurie (μCi) Electrical resistivity ohm meter (Ω-m) ohm inch (Ω-in.) ohm-centimeter (Ω-cm) ohm inch (Ω-in.) Thermal conductivity watt per centimeter per degree Celsius (watt/cm °C) International British thermal unit inch per hour per square foot per degree Fahrenheit (Btu in/h ft2 °F) watt per meter kelvin (W/m-K) International British thermal unit inch per hour per square foot per degree Fahrenheit (Btu in/h ft2 °F) Inch/Pound to International System of Units Length mil micrometer (µm) [or micron] inch (in.) centimeter (cm) inch (in.) millimeter (mm) foot (ft) meter (m) mile (mi) kilometer (km) Volume ounce, fluid (fl. oz) milliliter (mL) ounce, fluid (fl. oz) liter (L) Mass ounce, avoirdupois (oz) 28,350,000 microgram ounce, avoirdupois (oz) 28,350 milligram ounce, avoirdupois (oz) gram (g) ounce, troy 31.10 348 gram (g) ounce, troy 0.03110348 kilogram (kg) pound, avoirdupois (lb) kilogram (kg) ton, short (2,000 lb) ton, metric (t) ton, long (2,240 lb) ton, metric (t) Deposit grade ounce per short ton (2,000 lb) (oz/T) 34.285714 gram per metric ton (g/t) Energy kilowatthour (kWh) 3,600,000 joule (J) electronvolt (eV) 1.602 × 10-19 joule (J) Radioactivity microcurie (μCi) 37,000 becquerel (Bq) microcurie (μCi) kilobecquerel (kBq) Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F (1.8 × °C) + 32 Temperature in degrees Celsius (°C) may be converted to kelvin (K) as follows:

K °C + 273.15 Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C (°F - 32) / 1.8

Datum Unless otherwise stated, vertical and horizontal coordinate information is referenced to the World Geodetic System of 1984 (WGS 84). Altitude, as used in this report, refers to distance above the vertical datum. Supplemental Information Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C). Concentrations of chemical constituents in soils and (or) sediment are given in milligrams per kilogram (mg/kg), parts per million (ppm), or parts per billion (ppb). Concentrations of chemical constituents in water are given in milligrams per liter (mg/L), micrograms per liter (µg/L), nanogams per liter (ng/L), nanomoles per kilogram (nmol/kg), parts per million (ppm), parts per billion (ppb), or parts per trillion (ppt). Concentrations of suspended particulates in water are given in micrograms per gram (µg/g), milligrams per kilogram (mg/kg), or femtograms per gram (fg/g). Concentrations of chemicals in air are given in units of the mass of the chemical (milligrams, micrograms, nanograms, or picograms) per volume of air (cubic meter). Activities for radioactive constituents in air are given in microcuries per milliliter (μCi/mL). Deposit grades are commonly given in percent, grams per metric ton (g/t)—which is equivalent to parts per million (ppm)—or troy ounces per short ton (oz/T). Geologic ages are expressed in mega-annum (Ma, million years before present, or 10 6 years ago) or giga-annum (Ga, billion years before present, or 10 9 years ago). For ranges of years, "to" and (or) the en dash ("-") mean "up to and including." Concentration unit Equals milligram per kilogram (mg/kg) part per million microgram per gram (µg/g) part per million microgram per kilogram (μg/kg) part per billion (109) Equivalencies part per million (ppm): 1 ppm 1,000 ppb 1,000,000 ppt 0.0001 percent part per billion (ppb): 0.001 ppm 1 ppb 1,000 ppt 0.0000001 percent part per trillion (ppt): 0.000001 ppm 0.001 ppb 1 ppt 0.0000000001 percent Metric system prefixes tera- (T-) 1 trillion giga- (G-) 1 billion mega- (M-) 1 million kilo- (k-) 1 thousand hecto- (h-) 1 hundred deka- (da-) 1 ten deci- (d-) 10-1 1 tenth centi- (c-) 10-2 1 hundredth milli- (m-) 10-3 1 thousandth micro- (µ-) 10-6 1 millionth nano- (n-) 10-9 1 billionth pico- (p-) 10-12 1 trillionth femto- (f-) 10-15 1 quadrillionth atto- (a-) 10-18 1 quintillionth

Abbreviations and Symbols °C degree Celsius μm micrometer cm centimeter g/cm3 gram per cubic centimeter ISMI International Strategic Minerals Inventory kg/cm2 kilogram per square centimeter km kilometer m meter MRDS Mineral Resources Data System NIOSH National Institute for Occupational Safety and Health TWA time-weighted average

Graphite By Gilpin R. Robinson, Jr., Jane M. Hammarstrom, and Donald W. Olson Abstract Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. It has important properties, such as chemical inertness, thermal stability, high electrical conductivity, and lubricity (slipperiness) that make it suit­ able for many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. For some of these uses, no suitable substitutes are available. Steelmaking and refractory applications in metallurgy use the largest amount of produced graphite; however, emerging technology uses in large-scale fuel cell, battery, and lightweight high-strength composite applications could substantially increase world demand for graphite. Graphite ores are classified as "amorphous" (microcrystalline), and "crystalline" ("flake" or "lump or chip") based on the ore's crystallinity, grain-size, and morphology. All graphite deposits mined today formed from metamorphism of carbonaceous sedimentary rocks, and the ore type is determined by the geologic setting. Thermally metamorphosed coal is the usual source of amorphous graphite. Disseminated crystalline flake graphite is mined from carbonaceous metamorphic rocks, and lump or chip graphite is mined from veins in high-grade metamorphic regions. Because graphite is chemically inert and nontoxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dusts, including silicate and sulfide mineral particles, and hydrocarbon vapors produced during the mining and processing of ore. Synthetic graphite is manufactured from hydrocarbon sources using high-temperature heat treatment, and it is more expensive to produce than natural graphite. Production of natural graphite is dominated by China, India, and Brazil, which export graphite worldwide. China provides approximately 67 percent of worldwide output of natural graphite, and, as the dominant exporter, has the ability to set world prices. China has significant graphite reserves, and China's graphite production is expected to increase, although rising labor costs and some mine production problems are developing. China is expected to continue to be the dominant exporter for the near future. Mexico and Canada export graphite mainly to the United States, which has not had domestic production of natural graphite since the 1950s. Most graphite deposits in the United States are too small, low-grade, or remote to be of commercial value in the near future, and the likelihood of discovering larger, higher-grade, or favorably located domestic deposits is unlikely. The United States is a major producer of synthetic graphite. Introduction Graphite, which is a soft form of elemental carbon, is an industrial mineral commodity that is produced only in small amounts globally—worldwide production of approximately 1 million metric tons of graphite concentrate was reported as yearly production from 2010 to 2012 (Olson, 2012, 2013). The word graphite is derived from the Greek word for writing, graphein, which reflects the long use of graphite (mixed with clay) for the "lead" in pencils. The unique physical and chemical properties of graphite, particularly coarse crystalline graphite, make it useful for many industrial applications, and for some of those uses, no suitable substitutes are available. Although graphite is widely disseminated in many types of metamorphic and some igneous rocks, most occurrences have no economic importance. The significant deposits of graphite are found in carbonaceous sedimentary rocks that have been subjected to regional or contact metamorphism and in veins precipitated from fluids. Commercial Classifications of Graphite Sources of commercial graphite include both natural graphite mined from rock and synthetic graphite manufac­ tured from other carbonaceous materials. For commercial purposes, natural graphite is classified into the following three categories, according to its crystallinity, grain size, and morphology: amorphous, crystalline (flake), and crystalline (lump or chip). These commodity classes differ in the level of purity of the graphite, the proposed industrial use, the price, and the geologic setting in which the graphite occurs (table J1). Descriptions of (a) the graphite commodity classes and their industrial uses, and (b) their associated deposit types, geologic settings, and producing deposit locations are given

J2    Critical Mineral Resources of the United States — Graphite Table J1.  Characteristics of graphite commodities, deposits, and uses, by commodity type. [Descriptions of graphite commodity classes and their industrial uses, commodity prices, and classes of associated deposit types and geologic settings are summarized from information in Klar (1958), Weis (1973), Krauss and others (1988), Sutphin (1991a-c), Simandl and Kenan (1997a-c), Taylor (2006), and Olson (2011, 2012, 2013). NA, not applicable; µm, micrometer; cm, centimeter; °C, degree Celsius; m, meter; $, U.S. dollar] Characteristic Commodity type Amorphous Flake Lump or chip Synthetic Deposit type Amorphous Disseminated flake Vein NA Crystallinity Microcrystalline Crystalline Crystalline Microcrystalline to crystalline Properties (crystallinity, form) Earthy to compact micro­ crystalline aggregates; grain size is 4 μm Well-developed crystal platelets, with grain size between 40 μm and 4 cm (but generally ≤ 1 cm), and 1 to 150 μm thick Interlocking aggregates of coarse crystals. Available as powders to 10-cm pieces Available in particle sizes from 2-μm powders to 2-cm pieces Origin Contact metamorphism, often by diabasic or granitic intrusions, and (or) regional metamor­ phism of carbonaceous sediments, often coal Regional metamorphism of carbonaceous sedi­ ments at or exceeding amphibolite facies conditions Epigenetic veins and lodes formed from metamorphic fluids in high-grade metamorphic rocks, usually granulites Produced by heat treat­ ment (graphitization) of, or chemical deposi­ tion from, hydrocarbon materials above 2,100 °C Orebody Layers, seams, and lenses in carbonaceous rock, each a few meters thick and hundreds of meters to several kilometers in length; may be folded and faulted Strata-bound; tabular or lense form, as much as 33 m thick and thou­ sands of meters long. Irregular in hinge areas of folds. The lenses have variable graphite content internally and between lenses Vein and fracture-filling within or crosscutting metamorphic structures and rock contacts. Indi­ vidual veins range from 0.05 to 3 m thick, although usually less than 0.3 m, and extend up to hundreds of meters, although rarely more than tens of meters NA Ore grade (percent carbon) 50 to 90 (aggregates may contain nongraphitic carbonaceous material) Generally 5 to 30, locally higher 40 to 90 (may require hand sorting) NA Deposit tonnage (million metric tons) 0.1 to 500 0.1 to 100 Small; no reliable data for individual veins NA Mine operations Surface or underground mines using mecha­ nized and sometimes hand methods Generally open pit surface mines. Graphite grades and ease of mining enhanced by weather­ ing destruction of gangue minerals Mines are typically small, labor-intensive, and under­ ground. Mines in Sri Lanka are from 30 to 400 m deep. Ore is hand sorted, washed, and screened NA Product grade (percent graphite) 60 to 90 75 to 97 90 to 99.9 Main uses Refractories, steel industry, paint, coat­ ings, and batteries Refractories, brake linings, lubricants, batteries, and expandable graphite applications Carbon brushes, brake linings, and lubricants Batteries, carbon brushes, graphite electrodes, nuclear moderator rods (porosity unsuitable for refractory applications) Prices (per metric ton) December 2011 prices (80 - 85 percent graphite) ranged from $600 to $800 December 2011 prices (90% graphite, medium-large flake) ranged from $1,150 to $2,000 Prices in 2011 for Sri Lankan lump and chip graphite (99% graphite) ranged from $1,700 to $2,070. Prices vary by purity, grade, and size December 2011 prices (99.9 percent graphite) ranged from $7,000 to $20,000, which was about 4 to 7 times that of flake graphite Major producers and resources (in order of pro­ duction level) China, Republic of Korea, Mexico, Austria China, Brazil, India, Madagascar, Germany, Austria, Norway, Canada, Zimbabwe Sri Lanka China, Japan, United States, Germany (Roskill Information Services, Ltd., 2012)

Introduction    J3 by Klar (1958), Weis (1973), Krauss and others (1988), and Taylor (2006). Descriptive models of the geology and charac­ teristics of the deposit types that produce graphite are given by Sutphin and Bliss (1990), Sutphin (1991a-c), and Simandl and Kenan (1997a-c). A summary of information from these and other sources follows. Natural Graphite Natural graphite is mined from deposits in metamorphic rocks, such as marble, schist, and gneiss, and from accumu­ lations in vein deposits. Natural graphite typically forms as a result of metamorphism (regional or contact) of accumulations of organic matter in sedimentary rocks. Commercial deposits of graphite occur in three types of geologic settings that generally correspond to the following commodity classes (table J1): a. "Amorphous graphite" is the commercial designation for earthy to compact fine-grained graphite that generally results from thermal metamorphism of coal. Commercial deposits typically contain more than 1 million metric tons of ore that is more than 75 percent carbon. Both the raw ore and the commodity may contain nongraphitic carbonaceous material in addition to graphite. b. "Flake graphite" is the commercial designation for well-developed crystal platelets of graphite that are between 40 micrometers (μm) and 4 centimeters (cm— but generally less than or equal to 1 cm) in size and that are disseminated in beds of carbonaceous sedi­ ments that have been subjected to amphibolite-facies or higher grade regional metamorphism. Commercial deposits generally contain more than 200,000 metric tons of ore that grade greater than 8 percent graphite. Disseminated flake graphite deposits are located in belts of crystalline metamorphic rock that are predomi­ nately Archean to late Proterozoic in age. "Lump or chip" is the commercial designation for interlocking aggregates of coarse graphite crystals that occur as veins or fracture-fillings in igneous and crystalline metamorphic rocks that commonly are of Precambrian age. The only commercial deposits occur in Sri Lanka where families of veins that are up to 3 meters (m) thick and which consist of 60 to 95 percent graphite are mined to depths of 30 to 650 m (Touzain and others, 2010). The ore may be hand sorted to provide a product grade that exceeds 90 percent. No reliable data on the tonnages of individual vein deposits are available, but most of the deposits are small and likely do not exceed 100,000 metric tons. Synthetic Graphite Most of the graphite used by industries in the United States is synthetic. Synthetic graphite of high purity is produced by heat treatment (graphitization) of, or chemical deposition from, hydrocarbon materials above 2,100 degrees Celsius (°C). High-temperature processing is required to transform the precursor carbon forms to a graphite structure and to vaporize impurities, which include hydrogen, metals, nitrogen, organic compounds, and sulfur in the source materials. As a result of this treatment, synthetic graphite is more than 99.9 percent graphite, but it has slightly higher porosity, lower density, lower electrical conductivity, and a much higher price than natural flake graphite. Synthetic graphite is available in particle sizes ranging from 2-μm powders to 2-cm pieces; the morphology varies from flakey in fine powders to irregular grains and needles in coarser products. Uses and Applications Graphite has physical and chemical properties of both metals and nonmetals, which make it ideally suited for many industrial and technology applications. The metallic properties include high thermal and electrical conductivity (table J2). The nonmetallic properties include inertness to most chemical reagents (strong acids, bases, solvents, and fluxes), high thermal resistance, low thermal expansion, and excellent cleavage and lubricity (slipperiness). In a nonoxidizing atmosphere, graphite remains stable to temperatures above 3,000 °C. Graphite has a hardness of 1 to 2 on the Mohs scale and is thus extremely soft. Table J2.  Selected physical properties of graphite. [Modified from Krauss and others (1988). g/cm3, gram per cubic centimeter; °C, degree Celsius; watt/cm °C, watt per centimeter per degree Celsius; Ω-cm, ohm-centimeter] Property Description Composition Carbon Color Gray to black, metallic luster Hardness (Mohs scale) 0.5 to 1 Density (g/cm3) 2.09 to 2.26 Morphology Hexagonal system; perfect basal cleavage; usually platy Melting point About 3,550 °C in nonoxidizing conditions; decomposes above 600 °C in oxidizing conditions Miscellaneous Chemically inert; nontoxic; high ther­ mal and electrical conductivity; high lubricity (natural lubricant) Thermal conductivity (watt/cm °C) a axis: 4.0 c axis: 0.8 Thermal expansion coefficient (1/ °C) a axis: 1×10 -7 c axis: 140×10 -7 Electrical resistivity (Ω-cm×104) a axis: 1 to 100 c axis: 10,000

J4    Critical Mineral Resources of the United States — Graphite Some of the major end uses of graphite are in brake linings, refractories, and steelmaking. Batteries, brushes for electrical motors, foundry materials, fuel cells, and hightemperature lubricants are additional end uses of graphite. Graphite forms intercalation compounds with alkali metal vapors—usually potassium, lithium, rubidium, and cesium— where the metal ions fit between the planar carbon sheets of the graphite structure. These compounds have applications in the energy sector and other technologies. The industrial uses and associated commercial value of natural graphite depend on the characteristics and crystallinity of the mined graphite (table J1). Fine-grained microcrystalline graphite powder (amor­ phous graphite) is used extensively in foundry and refractory applications, as a source of carbon in steelmaking, and in other applications where additions of graphite improve the manufacturing process or end product. Coarse-grained crystalline graphite in the form of separate lamellar crystals (flake graphite) has high value and is used in high-temperature lubricants, high-quality foundry and refractory ware, powder metallurgy, coatings, and battery and fuel cell applications. Crystalline flake graphite accounted for about 50 percent of natural graphite usage in the United States in the past decade. Massive crystalline graphite from vein deposits (lump or chip graphite) has the highest purity and grain size of the natural graphite sold commercially. Because of its purity and crystallinity, many of the highest quality electrical motor brushes and other current-carrying carbon products use formulations of graphite from vein deposits. Synthetic graphite is used in many applications that require high-purity graphite, including anticorrosion products, batteries, carbon brushes, coatings, conductive fillers, elec­ trodes and electrolytic processes, fuel cell bipolar plates, and nuclear moderator rods. Synthetic graphite is unsuitable for foundry applications because of its increased porosity relative to natural graphite. Synthetic graphite is used in more applica­ tions in North America than natural graphite and accounts for a significant share of the graphite market. Demand and Availability of Supply No natural graphite was reported to have been mined in the United States in 2010 (Olson, 2012), and the major domestic sources of industrial graphite included imports of natural graphite, mostly from China, Mexico, Canada, Brazil, and Madagascar (in order of tonnage of imports), and synthetic graphite manufactured from carbonaceous materials. In 2010, 65,400 metric tons of natural graphite valued at an estimated $52 million was reported to have been imported into the United States for domestic consumption and 134,000 metric tons of synthetic graphite valued at an estimated $1.07 billion was reported to have been produced in the United States (Olson, 2012). Graphite Prices and Pricing Graphite is not traded on any commodity exchange. Commodity prices are subject to negotiation between buyer and seller and depend on carbon content, flake size and distribution (for crystalline flake), and the amount and nature of impurities. China is the dominant global natural graphite producer and has been the world price setter for decades. Four price series for graphite commodities based on production and value data reported by the U.S. Geological Survey (Olson, 2013) and Roskill Information Services, Ltd. (2012) are given in table J1. They are (a) microcrystalline (amorphous) graphite powder (from Mexico), which is currently in a long-term decline in importance because its low-technology end uses are becoming obsolete; (b) crystalline flake, which has become the most important natural graphite commodity in the past few decades and accounts for 80 to 90 percent of the value of U.S. imports of natural graphite; (c) lump graphite from Sri Lanka, which is a specialty product because its relatively high price results in low demand, and (d) synthetic graphite, which is a specialty product used primarily for applications that require high purity; its high price also limits demand. The price of microcrystalline (amorphous) graphite powder (80 to 85 percent carbon) ranged from $600 to $800 per metric ton in 2011; that of flake graphite (90 percent graphite) ranged from $1,150 to $2,000 per metric ton; Sri Lankan lump and chip graphite (99 percent graphite), from $1,700 to $2,070, depending on purity, grade, and particle size; and synthetic graphite (99.9 percent graphite), from $7,000 to $20,000 per metric ton, which is about four to seven times that of flake graphite (table J1). In 2010, graphite prices increased more rapidly for crystalline flake graphite than for amorphous graphite owing to increased demand for crystalline graphite used in friction material applications, such as brake linings, high-quality refractories, and lubricants, and in the manufacturing of graphite foils and long-life alkaline batteries (Industrial Minerals, 2010). Substitutes for Natural Graphite The most common substitutes for natural graphite are other forms of carbon. Manufactured synthetic graphite powders and graphite recovered from discarded foundry and manufactured materials can substitute for natural graphite in some applications, depending on the relative price. In steelmaking and some foundry applications, petroleum coke, anthracite, and synthetic graphite can be used instead of natural graphite. Synthetic graphite and natural graphite powder are commonly substituted for each other, or mixtures containing both kinds are prepared for customers (Taylor, 2006). Crystalline graphite is recovered from some foundry and refractory materials, although its recovery cost makes it noncompetitive relative to natural graphite for some applica­ tions (Weis, 1973; Olson, 2013).

Geology    J5 Strategic and Critical Resource Issues Graphite is considered a critical and strategic mineral because of its essential applications in the aerospace and energy sectors (such as refractory and foundry applications in the steel and metal industries and use in high-temperature lubricants, high-strength lightweight composite materials, batteries, modern nuclear reactors, fuel cells, electric motors, and evolving electronic applications that anticipate rapid growth in demand for graphite). The high concentration of resource supply from few countries could increase the commodity's susceptibility to market manipulation or disruption (Krauss and others, 1988; Taylor, 2006; European Commission, 2014). The United States has not produced natural graphite since the 1950s; China, Mexico, and Canada, in order of import supply, are the dominant sources of graphite imports to the United States (Olson, 2013). China has very low labor and production costs, and, with aggressive marketing, it established dominance in the world market in the 1980s (Taylor, 2006; Olson, 2013). China's graphite production is expected to increase and remain dominant in the world graphite market for the near future (Olson, 2013). China's rapidly growing domestic market for graphite may restrict future exports, however, which has raised concerns about possible supply shortages of graphite, particularly crystalline flake graphite, needed for anticipated large-scale fuel cell and battery applications; such applications could dramati­ cally increase world demand for graphite (Taylor, 2006; Olson, 2013; Olson and others, 2016). Graphite has played an important role in the emerging noncarbon energy sector and is used in several new energy applications. In energy production applications, graphite is used in pebbles for modular nuclear reactors and in highstrength composites for wind, tide, and wave turbines. In energy storage applications, graphite is used in bipolar plates for fuel cells and flow batteries, in anodes for lithium-ion batteries, in electrodes for supercapacitors, in high-strength composites for fly wheels, in phase change heat storage, and in solar boilers. In energy management applications, graphite is used in high-performance thermal insulation and in silicon chip heat-dissipation applications. These new energy applications commonly use specialty graphite products with such properties as extreme purity 99.9 percent graphite), very large or small (nano) particle size, and perfect crystal­ linity. Current graphite capacity may not be adequate for the increasing demands of these new energy applications, which, when fully implemented, may require double the current graphite supply, especially of high-purity crystalline flake graphite (O'Driscoll, 2010; Olson and others, 2016). Geology Geochemistry Carbon is the fourth most abundant element in the solar system, and in terms of its abundance in Earth's crust, is ranked about 12th to 17th in abundance, with an estimated crustal concentration between 180 and 270 parts per million. The abundance of carbon in Earth's crust is difficult to determine because carbon stores exist and cycle between rock, sediment, atmosphere, biosphere, and ocean reservoirs. The behavior of carbon in its geochemical cycle is influenced by the form in which the carbon occurs. Most of the carbon in Earth's crust (approximately 80 to 90 percent) is contained in carbonate minerals in carbonate rocks. Most of the remaining carbon in the Earth system occurs in living and fossil organic matter and as carbon dioxide (CO2 ) in the atmosphere or dissolved in the ocean. These remaining carbon forms dominate the carbon cycle. Graphite makes up only a small proportion of the carbon in Earth's crust, probably less than 0.5 percent, and much of this graphite likely formed by high-temperature thermal alteration of organic matter from biogenic sources deposited in sedimentary rocks and sub­surface reservoirs. The mineral graphite is stable and inert in the crustal environment and is unchanged under surface weathering conditions. Burial and thermal metamorphism tends only to recrystallize graphite. Therefore, graphite is largely isolated from the overall carbon cycle. Mineralogy Graphite is one of four forms of crystalline elemental carbon; the others are carbon nanotubes, diamond, and fullerenes. Graphite crystallizes in the hexagonal system, with rhombohedral symmetry, commonly forming six-sided tabular crystal flakes. It occurs naturally in metamorphic rocks and in some igneous rocks. Well-crystallized graphite flakes have a black metallic luster, whereas microcrystalline material is black and earthy with an amorphous appearance. The crystal structure of graphite consists of carbon atoms tightly arranged in parallel-stacked (c axis, fig. J1), planar honeycomb-lattice sheets (a axis, fig. J1). When the graphite structure is only a 1-atom-thick planar sheet, it is called graphene. The physical properties of graphite are listed in table J2. Many properties listed in table J2 vary by crystallographic orientation (a-axis and c-axis values, table J2) because of differences in bonding within (a axis, fig. J1) and between lattice sheets (c axis, fig. J1). The intraplanar (a axis) covalent bonding in graphite sheets is strong, but the electrostatic interlayer (c axis) forces holding the sheets together are weak, resulting in delocalized electrons that are free to move between sheets, which separates the sheets and allows them to

J6    Critical Mineral Resources of the United States — Graphite Figure J1.  Diagram showing the arrangement of carbon atoms in graphite, which consists of stacks of parallel sheets of carbon atoms (red circles in the figure), with each sheet containing hexagonal arrays of carbon atoms. Each carbon atom within a sheet is connected to its three nearest neighbors by covalent bonds that separate the atoms by a distance of 1.415 angstroms (Å) —an angstrom is one ten-billionth of a meter. The stacked sheets (shown here in their A and B orientation) are held together by weak intermolecular van der Waals' forces and are separated from each other by a distance of 3.354 Å. The arrangement of atoms defined by the dashed lines portrays one hexagonal (2H) unit cell of graphite. Modified from Kraus and others, 1989. Figure J6 - D a gram Sho wing th e Arrangement of Carbon Atoms in Graphite slide across one another easily. This gives graphite a density of 2.09 to 2.26 grams per cubic centimeter (g/cm 3), perfect basal (one-plane) cleavage, softness (0.5 to 1 on the Mohs scale), a greasy feel, and self-lubricating properties that make it useful as a lubricant. The ratio of force required to induce gliding of graphite sheets relative to compression force is low, resulting in high lubricity. These delocalized interlayer electrons also give graphite its high electrical and thermal conductivity. Graphite is the most electrically and thermally conductive of the nonmetallic elements (a-axis values, table J2); however, the intraplanar covalent bonds are very strong and require high energy to break them. These bonding properties make graphite chemically inert and physically stable at high temperatures (refractory). Graphite resists chemical attack by most reagents and is infusible in most common fluxes. Thermal oxidation of graphite in the presence of oxygen begins at about 300 °C, and the rate increases with temperature; however, it is stable in a nonoxidizing atmosphere to above 3,000 °C. Graphite sublimes between 3,300 °C and 3,500 °C at 1.033 kilograms per square centimeter (kg/cm2) and it melts at approximately 3,550 °C at a triple point under a pressure of 88 kg/cm2. Graphite is flexible but not elastic. All these properties combined make graphite desirable for many industrial applications. Deposit Types Natural graphite is a common constituent of meta­ sedimentary rocks and is mined in three geologic settings: (a) microcrystalline (amorphous) graphite deposits formed by metamorphism of coal, petroleum, or carbon-rich sediments, (b) disseminated flakes in metamorphic rock (flake graphite), and (c) graphite vein deposits (lump or chip graphite). Similar to most industrial mineral commodities, the economics of a deposit depend on its location and transportation costs to markets in addition to deposit grade, size, and mining charac­ teristics. Impurities in the deposit, such as silica, sulfides, or biotite, may limit the economic potential of a deposit. Amorphous Graphite Deposits Amorphous graphite deposits, which are formed by thermal metamorphism of coal, petroleum pools, or other highly carbonaceous sedimentary rocks, contain earthy to compact masses of microcrystalline graphite. Deposits may consist of multiple layers, seams, and lenses containing 50 to 90 percent carbon; each deposit is a few meters thick and up to a kilometer in length and lies within clastic metasedimentary rocks. The carbon content of amorphous deposits is dependent on the amount of carbon present in the original sediments, and the grade, tonnage, and purity of the deposit depend upon the characteristics of the precursor coal sequence or carbonaceous material. Deposits in metamorphosed massive coal seams may contain as much as 90 percent graphitic carbon, whereas deposits in other carbonaceous sediments or impure coal sequences commonly range from 25 to 60 percent carbon. Chemical and isotopic biomarkers found in natural graphite provide evidence of its origin from ancient biological material. Amorphous graphite deposits occur in geologic settings and environments where coal and other organicrich sedimentary rocks, such as oil shale, occur, including (a) shoreline, fluvial-deltaic, and alluvial fan depositional environments in passive continental margin settings, and (b) lacustrine and shallow inland seas and margins in foreland, continental, sag, or intracontinental rift basin settings. Host rocks include conglomerate, metagraywacke, quartzite, and schist. The thermal metamorphism is commonly caused by

Geology    J7 crosscutting diabasic or granitic intrusions with associated hornfels alteration of host rocks. Hornfels is a hard meta­ morphic rock formed by contact metamorphism of sedimen­ tary rocks close to intrusive igneous bodies. Graphite does not form until temperatures exceed 300 °C to 400 °C (Landis, 1971). The degree of metamorphism controls the degree of graphitization, and the ratio of graphite to nongraphitic carbon varies, but typically increases towards the heat source. Mineral impurities include meta-anthracite, anthracite, quartz, mica, pyrite, and other sulfides. Most currently mined deposits typically contain at least 80 percent carbon in deposits exceeding 1 million metric tons. The world's main sources of amorphous graphite are the metamorphosed coal deposits in Sonora, Mexico; Siberia, Russia; and the large coal province stretching from China into the Korean peninsula (table J3). The deposits in Sonora, Mexico, are the most significant deposits of amorphous graphite in the Western Hemisphere. They occur in a series of beds in an area 30 kilometers (km) long by 15 km wide located 60 km southeast of Hermosillo. In the district, the orebodies average 3 m in thickness, but deformation can produce seams up to 7 m wide. Grades exceed 75 percent contained graphite and some contain as much as 95 percent. The Moradillas deposit (Lourdes area, Mexico) has been reinterpreted as formed from a graphitized hydrocarbon protolith owing to its vein-like structure and lack of evidence that it is metamor­ phosed coal (Taylor, 2006). In the United States, small amor­ phous graphite deposits occur in metamorphosed coal deposits in the Narragansett Basin, Rhode Island, and in deposits in northern Michigan. An additional U.S. example occurs at Raton, New Mexico, where a basalt dike intersects a coal seam. Deposits of Flake Graphite Disseminated in Metasedimentary Rocks A large proportion of worldwide graphite production is derived from deposits of disseminated flake graphite found in metamorphic rocks, such as paragneiss (a gneiss derived from sedimentary rock), quartzite, and, sometimes, marble. These deposits formed when preexisting carbonaceous matter in the host sedimentary rock was converted to graphite during regional metamorphic conditions at or exceeding medium-pressure and medium-to-high-temperature condi­ tions (amphibolite facies). These metamorphic conditions are sufficient to crystallize fully ordered graphite (Hoefs and Frey, 1976) and recrystallize the rock matrix. The precursor host rocks of these deposits are interpreted as occurring in depositional settings where organic-rich sediments accumulate and are preserved. These settings include sediment-starved intracratonic and continental margin basins with low-oxygen conditions at depth to accumulate organic sediments, and periods of transgression (compare with, for example, Wilde and others, 1999), when sea level rises relative to land, preserving organic-rich sediments without erosion. The sedimentary rocks that are deposited during transgression may be deposited directly on existing basement rocks of the crust and are termed supracrustal rocks. The metamorphic conditions sufficient to form these deposits occur in the roots of continental mountain belts formed by deformation of Earth's crust, and significant postmetamorphic uplift and erosion are required to expose deposits in minable settings. Alumina-rich paragneiss, quartzites, and marbles at or near the highest grade of regional metamorphism at medium pressure (granulite facies) are favorable host rocks for flake graphite deposits because of their granular texture, coarse grain size, and low mica content. Supracrustal metasedimentary belts with these metamorphic features are termed crystalline metamorphic basement; their worldwide distribu­ tion has been mapped by Chorlton (2007). Most flake graphite deposits are located in Precambrian crystalline metamorphic basement (fig. J2), principally of Neoarchean to Proterozoic eras; however, deposits could occur in crystalline basement of any age. Precambrian supracrustal metamorphic belts appear to be more extensive, and metamorphosed to higher grades, than Phanerozoic belts (Chacko and others, 1987). The principal flake graphite deposits occur as stratabound lenses or layers; individual lenses in deposits are as much as tens of meters thick and hundreds of meters long. The lenses have variable graphite content, both within themselves and from one lens to another. The graphite content of a typical deposit varies from about 8 to 15 percent carbon, but the grade can vary from as low as 3 percent to about 60 percent carbon locally in individual deposits and between deposits. In Madagascar, one rich lens was reported to contain 60 percent graphite, and grades in the Kigluaik Mountains graphite district, Alaska, exceed 50 percent graphite in some areas (Coats, 1944). In paragneiss-hosted deposits, gangue (non-ore) minerals include in order of general abundance, feldspar, biotite, pyroxene, garnet, and sulfide minerals. Gangue minerals in carbonate-hosted deposits include calcite, pyroxene, feldspar, garnet, and sulfides. Flake graphite in crushed ore is separated from mineral impurities using washing, screening, flotation, and, sometimes, leach methods. The highest graphite grades commonly are associated with rock contacts between marble and paragneiss or quartzite, lenses in fault zones, in segregations within fold crests, and in structures that acted as channels for metamorphic fluids, all suggesting structural control of mineralization. Although most carbon in these deposits is thought to be present in the original sedimentary rocks, some carbon enrichment may be caused by processes involving internal or external buffering or mixing of metamorphic fluids (Lamb and Valley, 1984; Newton, 1986). Crystals in each deposit vary from a fraction of a milli­ meter to a few centimeters in size, usually reflecting the grain size in the parent rock. Most currently mined flake graphite deposits typically contain at least 8 to 12 percent graphitic carbon in deposits exceeding 0.5 million metric tons. Graphite is stable in the weathering environment; deposit grades and ease of mining are enhanced by weathering destruction of other minerals. Some deposits become so weathered that they can be mined with shovels and other hand tools.

J8    Critical Mineral Resources of the United States — Graphite Table J3.  Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Name Country State/Province Latitude Longitude Decimal degrees WGS 84 Quebrada Del Gato Argentina San Juan -31.43 -68.13 Undercliff Australia New South Wales -28.66 Jack's Creek Australia Queensland -20.67 Koppio-Uley mines Australia South Australia -34.80 Munglinup River Australia Western Australia -33.50 Doppl-Muehldorf-Zettlitz Austria Niederosterreich Kaisersberg-Trieben Austria Steiermark Itanhem Brazil Bahia -17.10 -40.35 Itapacerica Brazil Minas Gerais -20.43 -45.13 Pedra Azul Brazil Minas Gerais -15.88 -45.13 Bisset Creek Canada Ontario -78.07 Coronation Canada Ontario -77.94 Graphite Lake-Ryerson-Todd area Canada Ontario -79.08 Kirkham-Portland-Timmins area Canada Ontario -76.57 Tagliamonte Canada Ontario -78.07 Graphex-Graphico-Orwell Mines Canada Quebec -75.55 North American Mine Canada Quebec -75.55 St-Amime-Lac Des Iles Canada Quebec -75.53 Lac Knife Canada Quebec -61.18 Pollon Lake area Canada Saskatchewan -103.13 Haikou China Hainan Heling China Heilongjiang [Heilungkiang] Jixi (Liu Mao) China Heilongjiang [Heilungkiang] Liu Mao China Heilongjiang [Heilungkiang] Honan deposits China Henan [Honan] Hunan China Hunan Panshi China Jilin [Kirin] Hohot China Nei Mongol (Inner Mongolia) Shandong Peninsula China Shandong [Shantung] Xing He China — Kolledeye Czech Republic — Velke Vbrno-Konstantin Vvk Czech Republic — Kropfmühl-Cesky Krumlov Germany and Czech Republic Bayern [Bavaria, Germany]

Geology    J9 Table J3. Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Record type Ore type Operation Development status Tonnage Grade (% of carbon) District Site Site District District District District Site Site Site Site Site District District Site District Site Site Site District Site Site Site Site District District Site District District Site District Site District Crystalline (flake or lump?) Amorphous Amorphous Flake, weathering Flake Flake Amorphous Lump Flake, weathering Flake, weathering Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Amorphous Amorphous Flake Unknown Amorphous Amorphous Crystalline (flake or lump?) Flake Flake Flake Amorphous Flake Unknown Surface Surface,underground Surface,underground Surface,underground Surface Underground Surface Surface Surface Surface Unknown Surface Surface Surface Surface Unknown Surface Surface Unknown Surface Unknown Surface Unknown Unknown Underground Underground Surface Surface Unknown Surface,underground Surface Underground Producer Past producer Past producer Past producer Past producer Producer Producer Producer Producer Producer Prospect Occurrence Producer Producer Prospect Producer Past producer Producer Prospect Past producer Producer Producer Past producer Producer Producer Producer Producer Producer Producer Producer Prospect Producer Producer — 2,200 35,030 30,000 1,000,000 1,000,000 2,778 383,000 26,800,000 4,938,000 — Large 478,000 — 2,200,000 — — 4,900,000 1,663,000 5,000,000 — 300,000,000 3,000,000 — — — — 5,900,000 — — 200,000 — — — — — — — — — — — — — —

J10    Critical Mineral Resources of the United States — Graphite Table J3.  Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Name Country State/Province Latitude Longitude Decimal degrees WGS 84 East Godavari India Andhra Pradesh Khammam India Andhra Pradesh Srikakulam India Andhra Pradesh Visakhapatnam India Andhra Pradesh Khamdih India Bihar Sokra India Bihar Dandatapa area India Odisha Sargipali area India Odisha Titlagarh area India Odisha Tumdibandh-Phulbani area India Odisha Tamatia mines India Rajasthan Madurai India Tamil Nadu [Madras] Chawia Kenya — -3.46 Oldoinyo-Nyiro Kenya — Yonghung-Kaechon area Korea, North Hamgyong-Namdo Songjin deposits Korea, North Hwanghae-Namdo Wolmyong-Kaerim-Pongmyong Korea, Republic of Ch'Ungch'Ong-Bukto Yongwon-GunJa-Pyongtack-Shihung Korea, Republic of Ch'Ungch'Ong-Namdo Ampangadiatany Madagascar Toamasina -19.41 Ambatomitamba Sahanovo area Madagascar Toamasina -18.35 Perinet-Ambatovy area Madagascar — -18.93 Vatomandry area Madagascar — -19.34 Telixtlahuaca Mexico Oaxaca -96.86 Las Trincheras Mexico Sonora -111.53 Lourdes area Mexico Sonora -110.50 Tonichi Mexico Sonora -109.57 Skaland-Senja Norway — La Galgada-La Limena-San Carlos Mines Peru Ancash -8.46 -78.13 Baia De Fier Romania — Botogolsk Russia Buryatiya Boyarsk Russia Buryatiya Kureyka Russia Krasnodarskiy Kray Noginskoje Russia Krasnodarskiy Kray Soyusnoye Russia — Tayginsk Russia — Gumbu graphite mine South Africa — -22.32 Malonga graphite mine South Africa — -22.65 Kahatagaha-Kolongaha mines Sri Lanka —

Geology    J11 Table J3. Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Record type Ore type Operation Development status Tonnage Grade (% of carbon) District District District District District District District District District District District District District Site District District District District Site District District District Site Site District Site Site District Site Site District Site Site Site Site Site Site District Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake, lump Flake Flake, lump Flake, weathering Flake, weathering Amorphous Flake Amorphous Flake, weathering Flake, weathering Flake, weathering Flake, weathering Flake, weathering Flake, weathering Amorphous Amorphous Amorphous Flake Amorphous Amorphous Lump, flake Flake Amorphous Amorphous Flake Flake Flake Amorphous Lump Surface Surface,underground Unknown Surface Surface Surface Surface Surface Surface Surface Surface Surface Surface Surface Surface,underground Unknown Underground Surface Surface Surface Surface Surface Surface Underground Underground Unknown Underground Unknown Surface,underground Underground Unknown Surface,underground Underground Surface Surface Unknown Surface Underground Producer Producer Producer Producer Producer Producer Producer Producer Producer Producer Producer Producer Past producer Prospect Producer Producer Producer Producer Past producer Producer Producer Producer Producer Producer Producer Producer Producer Past producer Past producer Producer Past producer Producer Producer Producer Producer Past producer Past producer Producer — — — — — — — — — — 1,120,000 130,000 — 1,200,000 — — 12,000,000 1,400,000 — 2,000,000 — 2,000,000 13,400,000 — 2,000,000 2,000,000 2,000,000 — 58,000 Small Large 87,000,000 10,000,000 8,200,000 1,116,000 — 20,000,000 100,000 — — — — — — — — — — — — — — — — — — —

J12    Critical Mineral Resources of the United States — Graphite Table J3.  Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Name Country State/Province Latitude Longitude Decimal degrees WGS 84 Zavalyevskiy Ukraine — Clay-Coosa-Chilton graphite district United States Alabama -85.84 Christophosen Creek United States Alaska -165.63 Graphite Creek United States Alaska -165.54 Imuruk Basin Graphite United States Alaska -165.55 Kigluaik Mountains graphite district United States Alaska -165.54 Southern California area United States California -118.47 Black Lady Nos. 1 and 2 United States California -118.07 Eureka Plumbago-Morgan mines United States California -120.38 Skinner Ranch United States California -122.59 Unnamed United States California -121.56 Unnamed United States California -123.77 Wedge United States California -115.98 Graphite Basin United States Colorado -106.38 Unnamed graphite deposit United States Colorado -105.98 Graphite mines United States Connecticut -73.37 Lead Hill Mine graphite deposits United States Connecticut -72.18 Unnamed graphite mine United States Georgia -84.74 Detroit-Northern Graphite quarries United States Michigan -88.35 Black Diamond Carbon Graphite United States Montana -111.63 Crystal Graphite Mine United States Montana -112.51 Boston-Goshen-Osgood Mines area United States New Hampshire -72.10 Stone Mills Graphite Mine United States New Jersey -74.88 Adirondack Mining & Milling Mine United States New York -73.46 Essex-Warren area United States New York -73.47 Champlain Graphite Mine United States New York -73.48 M. B. Hooper Graphite Mine United States New York -73.50 Pope Mills-Rossie deposits United States New York -75.55 Rowland Graphite Mine area United States New York -73.97 Silver Leaf Graphite Co. Mine United States New York -73.43 Dillinger Mine and mill United States North Carolina -82.18 Cranston-Penners Ledge Mines United States Rhode Island -71.46 Copper Cliff Mine United States South Dakota -103.84 Burnet-Llano district United States Texas -98.36 Rabbit Creek area United States Wyoming -105.23 Taskazgan Uzbekistan — Lynx Mine Zimbabwe — -16.43

Geology    J13 Table J3. Location, grade, tonnage and other data for selected graphite deposits and districts of the world.—Continued [The names, locations, and descriptions of most of the deposits are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS; U.S. Geological Survey, 2012). Identification number is keyed to the deposits shown in figure J2. Negative values for latitude indicate that the deposit is in the Southern Hemisphere; negative values for longitude indicate that the deposit is in the Western Hemisphere. Record types are from the MRDS. Ore type is characterized as amorphous, crystalline, flake, or lump (includes chip), as defined in table J1. "Weathering" indicates surface ores that have been deeply weathered, which lowers mining costs. Development status of the deposit is given as follows: Current, current or recent mine activity; Past, past producer with no current mining; Prospect, an unmined deposit with characterized resources; Occurrence, an unmined deposit with uncharacterized resources. Tonnage of ore has been updated from the values in the MRDS and is given in metric tons or, alternatively, is categorized as large (likely exceeds 1 million metric tons but is not well characterized) or small (likely is less than 100,000 metric tons). %, percent; —, unknown; WGS 84, World Geodetic System of 1984] Identification number Record type Ore type Operation Development status Tonnage Grade (% of carbon) Site District Site Site Site District District Site District Site Site Site Site District Site Site Site Site Site Site Site District Site Site District Site Site District District Site Site District Site District Site Site Site Flake, weathering Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Flake Lump or flake Lump or flake Flake Amorphous Flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Lump or flake Flake Amorphous Flake Flake Flake Flake Flake Surface Unknown Unknown Unknown Surface Unknown Surface Surface Unknown Surface Unknown Unknown Unknown Underground Unknown Surface Surface Surface Surface Surface Unknown Surface Unknown Surface Surface-Underground Surface Underground Underground Surface-Underground Surface Surface Unknown Unknown Unknown Underground Surface Underground Producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Past producer Producer Producer? 100,000,000 300,000 65,000 — — 10,000,000 — — — — — — — — — Small Small — — — — — — — — — — — — — — — — 400,000 — 2,300,000 6,700,000 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —

J14    Critical Mineral Resources of the United States — Graphite Figu re J Wo rl d M ap Show ing Loc ati ons of Ma jor G rap hit e D epo sit s ifier number in table J3. World map showing locations of major graphite deposits and districts in the world, by commodity type. Numbers refer to the ident

Figure J2. Distribution of crystalline metamorphic basement is from Chorlton (2007).

Geology    J15 The world's main sources of crystalline flake graphite are the deposits in Brazil, Canada, China, India, and Madagascar. Probably the largest resources of high-grade crystalline flake graphite in the world are in China (Jixi district) and the island country of Madagascar. The deposits in both areas occur in belts of Neoarchean to late Proterozoic micaceous gneiss and schist that are interpreted to be associated with a series of mountain-building events related to the formation of the Gondwana supercontinent about 600 million years ago (Wilde and others, 1999), named the Pan-African orogeny. Pan-African age supracrustal metamorphic belts also occur in areas in Western Australia, eastern India, and Sri Lanka; these areas also host significant flake graphite deposits located in the most productive graphite-bearing regions of the world (fig. J2). Graphite-rich horizons in Madagascar occur over a distance of more than 800 km in the eastern half of the island. Individual deposits are graphite-rich layers that range from 3 m to more than 35 m in thickness and extend up to a few kilometers. Ore grades average 4 to 10 percent graphite, but grades are reported to be as high as 60 percent in some areas. The flake graphite deposits in the State of Minas Gerais, Brazil, are mined from graphite-bearing soils overlying extensively weathered host rock with grades of 12 to 16 percent graphite; the ore is mined by front-end loader or shovel. Shandong Province in China is a major flake graphite producer. The flake graphite deposits in the vicinity of Jixi, China, are mined from deformed lenses and discordant layers of graphite schist and gneiss in paragneiss; graphite content ranges from 15 percent in the gneiss to up to 45 percent in the schists, with local flake graphite resources exceeding 360 million metric tons (Wilde and others, 1999). Little is known about the deposits in Russia and India. Large disseminated flake graphite deposits occur at a number of places in the Grenville Province metamorphic belt in Canada's Quebec and southeastern Ontario Provinces, and small deposits associated with Grenville series marble, gneiss, and pegmatites also occur in the Adirondack Mountains west and northwest of Ticonderoga, New York (Alling, 1918). The Grenville Province is a southwest-trending belt of deformed high-grade supracrustal metamorphic rocks of Mesoproterozoic age that is exposed across 2,000 km from Labrador, through Quebec, into southeastern Ontario, and continues in the subsurface a further 3,000 km to Texas and Mexico. The Lac Knife graphite deposit at Fermont, Quebec, has high-grade ore hosted by migmatized quartz-feldspar (biotite) gneiss. The host rock is the southern extension of carbonaceous shales and sandstones that have been deformed and metamorphosed in the crosscutting Grenville Province metamorphic belt. Deposits of flake graphite in the United States have been mined in Alabama, Alaska, and Texas. The deposits of the Clay-Coosa-Chilton graphite district, Alabama, occur in two parallel layers and lenses in the Ashland quartz-mica schist that contain 1 to 5 percent disseminated flake graphite (Pallister and Thoenin, 1948). The layers and lenses range from 6 m to more than 35 m in thickness, dip gently, and occur in a northeast-trending 1- to 3-km-wide belt that extends for more than 90 km. The deposits are weathered to depths of 35 m. The deposits in the Burnet-Llano district, Texas, occur in the Precambrian Packsaddle schist and show a wide range of graphite content and flake size (Needham, 1946). The graphite flake deposits in the Kigluaik Mountains graphite district, Alaska (Coats, 1944) represent the largest known domestic graphite resource, but are located in a rugged and remote area with high mining costs. Vein Deposits Containing Lump or Chip Graphite Crystalline graphite of the lump or chip commodity type is generally found in well-defined veins composed almost entirely of graphite that cut high-grade metamorphic rocks or as accumulations along intrusive contacts of pegmatites with marbles or paragneiss. The veins form in high-grade regional metamorphic environments where metasedimentary belts are invaded by igneous rocks. In some areas, the veins are local­ ized in granulite-facies domains within the broader regional metamorphic belt (Chamberlain and Rumble, 1988). Graphite-bearing veins form within or crosscut meta­ morphic structures, rock contacts, and folds. The veins range from thin films to massive bodies that are more than 3 m thick and may extend for hundreds of meters, although they usually extend for less than tens of meters. The veins consist largely of coarse, platy, or needlelike interlocking crystals of graphite. Mineral impurities depend largely upon the host rock; quartz, feldspar, pyroxene, and calcite are common. Ore grades range from 40 to more than 90 percent graphitic carbon; the percentage largely depends on the amount of wallrock contained with the ore material. Hand sorting may be required to provide lump concentrates of high purity. Graphite vein deposits are found in similar settings as disseminated flake graphite deposits, and they may be spatially associated with them. The Sri Lankan graphite deposits, which are the only economically significant examples of the vein-type deposits, occur in high-grade metamorphic rocks of Neoarchean to Proterozoic age. Most vein deposits and prospects occur in crystalline metamorphic basement rocks of Neoarchean to late Proterozoic age, although deposits may be of any age. The graphite in these deposits occurs as veins in fractures and structures that are emplaced near or after peak metamorphic conditions. It is clear that the carbon in the vein deposits has been transported by metamorphic or replacement processes, presumably aided by metamorphic or other fluids; however, the nature of the processes responsible for the precipitation of graphite in the veins is uncertain and controversial, and may vary between deposits. Most veins are hosted in high-grade metamorphic rocks; however, graphite precipitation may take place after the most intense deformation and thermal conditions of regional metamorphism have been achieved, as suggested by the localization of veins in brittle structures that are not disturbed by penetrative deformation associated with metamorphism and veins that crosscut syntectonic intrusives

J16    Critical Mineral Resources of the United States — Graphite (Rumble and Hoering, 1986; Rumble and others, 1986). In some veins, low-temperature minerals, such as prehnite, occur with graphite. Textural evidence and age determinations on zircon inclusion rims in graphite (Zeitler and others, 1990), however, indicate that some veins were emplaced during or soon after peak metamorphic conditions and that the hydro­ thermal systems responsible for vein formation may also be responsible for the high-grade metamorphic conditions found in their immediate vicinity (Chamberlain and Rumble, 1988). Carbon isotope studies of the vein deposits show a wide range in isotopic composition between and within districts; this variation may be explained by varying carbon sources from two crustal reservoirs: (a) reduced biogenic carbon, and (b) carbonate minerals (Rumble and Hoering, 1986). The most probable processes resulting in graphite precipitation in veins likely include rock-fluid redox reactions, such as oxidation of methane (CH4 )-bearing fluids or reduction of CO2-bearing fluids by wall rock (internal or external buffering), cooling of hot fluids saturated with respect to graphite, and mixing of fluids with differing CH4 and CO2 contents (Rumble and others, 1986). The United States has small graphite vein deposits in New Hampshire, Connecticut, the Adirondacks of New York, and Montana; these deposits are largely of only scientific interest. The Crystal Graphite Mine near Dillon, Montana, is the largest known graphite vein deposit in the United States. At this deposit, veins up to 60 cm thick and 15 m long occur in fractures in gneiss and pegmatite (Bastin, 1912); the fractures and veins formed after the peak of metamorphism in these rocks (Ford, 1954). Mining and Beneficiation Methods Natural graphite is mined from both open pit and underground mine operations (table J3). Production from open pit operations is less expensive and is preferred where the overburden can be removed economically. Most crystalline flake deposits are mined using open pit methods; the excep­ tion is some steeply dipping bodies with high-grade minable lenses containing 15 percent or more contained carbon (table J3). Graphite is stable in the weathering environment, and intensely weathered crystalline flake deposits, such as those in Brazil, Kenya, Madagascar, and Oaxaca, Mexico, can be easily and profitably mined using open pit methods. Underground mining methods are used in some amorphous deposits in China, Europe, the Republic of Korea, and Mexico, and vein deposits in Sri Lanka, where the ore intervals are deep and of high grade (>80 percent contained carbon). Beneficiation processes for graphite vary from simple hand sorting and screening of high-grade ore at some amorphous graphite deposits and at the Sri Lankan vein operations to multistage crushing, screening, washing, and flotation cycles required to produce high-quality and high-purity graphite flake and powder products. No refining of amorphous graphite ore is needed for most uses. Resources and Production Distribution of Graphite Deposits and Districts The world map in figure J2 shows the location of 108 natural graphite deposits and districts characterized as: (a) amorphous deposits that result from thermal or contact metamorphism of highly carbonaceous sediments, usually graphitized coal beds, or (b) crystalline deposits of either disseminated flake graphite, which have resulted from regional metamorphism of carbonaceous sediments under conditions exceeding amphibolite facies, or coarse graphite aggregates (lump or chip) in fracture-filling veins cutting igneous and metamorphic rocks. Both of the crystalline deposit types (flake, or lump and chip) are mostly located in crystalline metamorphic bedrock (fig. J2), consisting primarily of coarsegrained quartzofeldspathic metasedimentary rocks at high metamorphic grades (Chorlton, 2007). Table J3 describes the features of the 108 natural graphite deposits and districts shown in figure J2 that are known to have produced graphite or are significant prospects with potential for future development. A number of deposits and districts with past production, particularly those in the United States, have grade and tonnage characteristics that render the deposits subeconomic under current conditions; these are included to identify broad areas and regions that may be future sources of graphite production or may contain undiscovered deposits. The names, locations, and descriptions of most of the deposits in table J3 are taken from the International Strategic Minerals Inventory (ISMI) graphite inventory (Krauss and others, 1988) and the U.S. Geological Survey Mineral Resources Data System (MRDS) (U.S. Geological Survey, 2012). Figure J3 shows the deposit grade (percent carbon) and tonnage reported for some of the deposits in table J3, characterized by deposit type. The lowest tonnage and grade deposits in figure J3 are Fi gur e J Pl ot of Gra de and Ton na ge Figure J3.  Plot of grade (carbon) and tonnage for some of the amorphous and crystalline graphite deposits listed in table J3, by deposit type. The table also gives additional resource data, and sources.

Resources and Production    J17 subeconomic under current market conditions; typical ranges of commercial grades and deposit tonnage, by commodity type, are given in table J1. World Graphite Production and Resources Natural graphite is produced by more than 20 nations, but world production is dominated by China, India, and Brazil. Figure J4 shows the average level and amounts of natural graphite produced worldwide by area from 2006 to 2010, based on data from Olson (2011). During this period, China accounted for approximately 67 percent of worldwide produc­ tion of natural graphite, and established itself as the dominant exporter with the ability to set world prices. China became a major global supplier of graphite in the 1980s owing in part to very low production costs and aggressive marketing. India and Brazil are significant worldwide exporters of graphite whereas Mexico and Canada export mainly to the United States. Global graphite resources are large relative to annual global consumption, and undoubtedly extensive, but their extent is poorly known because resources of industrial mineral commodities typically are not fully delineated and reported far in advance of development. Complete estimates of graphite resources are likely not available for any single major graphite district in the world. Table J4 tabulates conservative estimates for recoverable graphite resources for a number of major graphite-producing nations. Reserves of natural graphite (that is, the identified, delineated, and reported world resources that are considered to warrant economic exploitation at the time of reserve determination) are equivalent to 81 million metric tons. Approximately 26 percent of reserves are crystalline (flake and vein type [lump or chip]) graphite materials for which demand is increasing. Other identified resources beyond reserves ("Other identified resources" in table J4) are about an additional 1.4 billion metric tons, leading to an estimate of total identified graphite resources of approximately 1.5 billion metric tons worldwide. Approximately one-half of this total resource estimate is flake graphite. Future exploration is likely to result in the discovery of world resources that are many times this estimate; however, many new discoveries are likely to be located in remote areas with high mining costs and limited access to infrastructure and industrial markets that use graphite. The Lac Knife deposit in Quebec, Canada, is an example of a relatively recent discovery in a remote setting (Bonneau and Raby, 1990). Future discoveries of amorphous and flake graphite deposits in the conterminous United States are likely to be limited by favorable geology and preexisting exploration coverage. The coal fields of the United States are well explored and delineated, and past igneous activity in the coal­ fields is either absent or of such limited scale that the chance of finding amorphous graphite deposits of commercial size and grade is negligible. Furthermore, with the exception of Alaska, crystalline metamorphic rocks that could potentially host flake and vein (lump or chip) graphite deposits have limited extent and exposure in the United States, and most of the crystalline basement that is present is well characterized. The identified flake graphite deposits in the Kigluaik Mountains of Alaska indicate potential for additional deposits in surrounding areas; however, these are likely to occur in remote areas with rugged terrain and limited infrastructure, and such deposits would be a great distance from graphite markets and have high mining costs. The weathered low-grade crystalline flake deposit districts in Alabama and Texas may provide future domestic sources of graphite if flake graphite prices increase, because of the ease of mining the deposits and their proximity to markets. Figure J4 - Pie Chart Sho wing Average Annual Natural G raphite Produ ction Figure J4.  Pie chart showing average annual natural graphite production for the period 2006-10, by country or region and amount (in thousand metric tons [kt]). The tonnages are estimated based on data reported in Olson (2011).

J18    Critical Mineral Resources of the United States — Graphite Table J4.  Estimates of world graphite resources, by country, commodity type, and resource category, in thousand metric tons of recoverable graphite. [Resources reported for recoverable amorphous, flake, or crystalline (vein-type) commodity categories. Resource categories: (a) Reserves are demonstrated resources of recoverable natural graphite considered to warrant economic exploitation at the time of reserve determination; (b) Other identified resources are estimates of characterized recoverable resources beyond those reported as reserves; only part of this estimate would be economic; and, (c) Total identified resources includes reserves and other identified resources. Data are adapted from Olson (2013) and Taylor (2006) and rounded to two significant figures. NA, not available] Country Type Reserves Other identified resources Total identified resources1 Austria Amorphous 1,100 1,200 Brazil Flake 3,400 3,800 Canada Flake 1,500 4,200 5,700 China Amorphous 55,000 NA NA Flake 6,000 350,000 360,000 Czech Republic Flake 12,000 13,000 Germany Flake India Flake 13,000 14,000 Madagascar Flake 180,000 180,000 Mexico Amorphous 3,100 10,000 13,000 Flake North Korea Amorphous 1,000 30,000 31,000 Flake 1,400 2,100 Norway Flake Republic of Korea Amorphous 2,100 2,100 Flake Romania Amorphous NA Russia, with Ukraine Amorphous 1,000 560,000 560,000 Flake 6,400 94,000 100,000 Sri Lanka Crystalline, vein Flake 1,800 7,000 8,800 United States2 Amorphous 5,900 5,900 Flake Zimbabwe Flake 1,200 1,800 Other Flake 1,200 Total Amorphous 60,000 750,000 810,000 Total Flake 21,000 670,000 690,000 Total Crystalline, vein Total By resource category 81,000 1,400,000 1,500,000 1 Total identified resources includes reserves and other identified resources. 2 Other identified resources includes Alabama, Alaska, and New York.

Environmental Considerations    J19 Exploration for New Deposits Prospecting for graphite deposits consists primarily of outcrop examination, trenching, and sampling, usually followed by drilling. Because of its chemical inertness, graphite resists weathering, and outcrops containing graphite and residual soils containing conspicuous graphite flakes may be evident. Knowledge of areal geology and the geologic features and settings of different graphite deposit types and associated deposits, such as coal, can be used to identify promising exploration targets. The Lac Knife flake graphite deposit was initially discovered during routine geologic mapping. When interest developed, the prospect was trenched by shovel, followed by further surface excavation, and later systematically characterized at depth by more than 99 drill holes. All this activity occurred during a more than 30-year time period (Bonneau and Raby, 1990). Because of the high electrical conductivity of graphite (in deposits where individual graphite flakes are touching), a variety of electromagnetic methods have been used to search for deposits, principally flake graphite deposits. Electro-magnetic geophysical methods measure variations in the electrical conductivity of the ground caused by changes in mineral content, properties, or subsurface features. The methods rely on the process of electromagnetic induction that describes how a conductive material, such as graphite, will interact with a magnetic field. Surveys are conducted by using either surface or airborne methods; all methods use a transmitter and receiver coil spaced in standard configurations. The different methods use different operating frequencies to provide a range of depth penetrations and resolution needed for different applications. High-frequency electromagnetic systems are best for locating small shallow targets; lower frequency systems are used to investigate deeper subsurface conditions or define regional targets. The relative merits of various geophysical techniques in detecting graphite deposits are discussed by Goosens (1982, p. 136). Graphite flakes may be found in stream sediment samples collected during exploration geochemical surveys. The pres­ ence of sulfides and vanadium-bearing garnet (goldmanite) may also be an indicator. There is a positive correlation between carbon, uranium, and vanadium contents in some deposits (Li and others, 1985), and positive vanadium, nickel, and (or) uranium anomalies in soil associated with graphite beds were reported by Tichy and Turnovec (1978) and may be considered a geochemical indicator of graphite deposits. These geochemical features probably relate to the depositional environment and trace element content of the protolith and likely vary among deposits. Therefore, it may be difficult to use these features effectively in grassroots exploration for graphite deposits. Environmental Considerations Because of the chemically inert, nontoxic nature of graphite, the main environmental concerns associated with graphite mining are (a) the presence of other minerals that can occur with graphite, and (b) inhalation of graphite particles or fine-grained silica minerals in graphite during mining and processing. For example, the iron sulfide minerals pyrite and pyrrhotite are present in amounts ranging from a trace to several percent in some graphite deposits. These minerals can cause acid-rock drainage if exposed to air and water in waste rock or tailings. Graphite in soils and stream or river sedi­ ments is inert and poses no known terrestrial or aquatic risks. Mine Waste Characteristics The volumes and mineralogical characteristics of mine wastes depend on the size and type of deposit, as well as the mining and processing practices employed. For open pit mines, the amount of overburden that must be stripped prior to the onset of mining contributes to the mine waste. Ore processing for disseminated flake graphite typically includes milling, flotation, screening, and drying. The resulting mine waste and flotation tailings are composed of the minerals that make up the host rocks, typically schists and gneisses composed mainly of quartz and feldspars. Other silicate minerals in these rocks include pyroxenes, amphiboles, micas, garnet, and sillimanite. These are all moderate- or slow-weathering minerals (Jambor, 2003). Quartz persists in the environment, whereas feldspars weather to clays. Fast-weathering, potentially acid-producing sulfide minerals, such as pyrite and pyrrhotite, are reported at some deposits. The yellow iron sulfate mineral jarosite, which is an indicator of acidic conditions, is a common weathering product of pyritic, gneiss-hosted graphite deposits (Simandl and Kenan, 1997b). Calcite and other carbonate minerals may be present in gangue and can provide acid neutralization if present in sufficient amounts. The largest known flake graphite deposit, the Zavalyevskiy deposit in Ukraine, has total resources on the order of 100 million metric tons with reserves of 6.4 million metric tons containing 5 to 7 percent graphite (Zavalyevskiy Graphite Ltd., 2013). The ore is kaolinized gneiss that contains garnet, biotite, chlorite, pyroxene, quartz, and sillimanite. Both garnet and crushed stone products are recovered from the ore. The graphite ore is processed by flotation to produce a high-purity graphite concentrate (86 to 97 percent graphite) and ash (10 to 13 percent graphite). Graphite orebodies in graphite schist at the Liu Mao Mine in China are elevated in vanadium (0.2 percent vanadium pentoxide [V2O5 ]), titanium (0.5 percent titanium dioxide [TiO2 ]), and uranium (0.004 percent U). These elemental concentrations

J20    Critical Mineral Resources of the United States — Graphite are attributed to garnet intergrown with graphite in the deposit (Wilde and others, 1999). In Canada, a composite grab sample for metallurgical testing at the Trout Lake (also known as Treelined Lake) graphite prospect in southern Ontario contains 1.8 percent sulfur, which is attributed to 4.5 percent pyrrhotite in the sample; the preliminary test indicated that pyrrhotite removal by screening and flotation would be required to obtain a salable graphite product (Kuehnbaum and Zebruck, 2002). At the Bissett Creek flake graphite deposit in Ontario, both ore and waste rock are recognized as potential acid generators (Systèmes Gèostat International Inc., 2007). The graphite occurs in a calcareous biotite-amphibole-quartzofeldspathic gneiss with disseminated graphite, pyrite, pyrrhotite, and trace chalcopyrite. Graphite concentrations range from about 1 to 10 percent; the sulfide minerals constitute 1 to 5 percent of the rock. Mine plans call for underwater tailings storage and the addition of carbonate-bearing material to the waste dump to neutralize acid potential. In contrast, at the Eagle deposit in British Columbia, high-purity flake graphite is quarried from quartz-rich sands, and slightly alkaline sand and aggregate byproducts are marketed as construction materials. Amorphous graphite deposits range from about 300 to 800 million metric tons of ore and have higher average graphite grades than other types of graphite deposits (table J1). The ore is essentially the entire graphitized unit. The associ­ ated waste primarily is any overburden that must be removed to access the deposit. Mineral impurities in amorphous graphite deposits reflect the compositions of the protolith coal or sediment (Simandl and Kenan, 1997a). In the Bohemia region of the Czech Republic, elevated concentrations of vanadium and nickel anomalies are associated with amorphous graphite deposits (Tichy and Turnovec, 1978). Waste material described as graphite gangue at the Jixi deposit in China contains zinc, nickel, and mercury (Liu and Man, 2007). Vein graphite from Sri Lanka, which is significant for its purity and high degree of crystallinity, is mined underground at the Bogala Mine (370 m deep) and Kahatagaha-Kolongaha Mine (650 m deep). Total inferred reserves for these two mines are about 400,000 metric tons. At these mines, graphite veins are blasted with dynamite. When the fumes clear, the ore is hauled to the surface and then hand cobbed and graded; no further processing is required, so no tailings or large waste piles are produced (Ranasinha and Uragoda, 1972). Hydrothermal minerals associated with the graphite from Sri Lanka include apatite, biotite, calcite, chalcopyrite, pyrite, and quartz. The average chemical contents reported for different vein graphite morphologies from the Bogala and the Kahatagaha-Kolongaha Mines reported by Touzain and others (2010) are as follows: 93 to 99 percent carbon, 0.06 to 1.06 percent iron oxide (Fe2O3), 0.05 to 0.45 percent silicon dioxide (SiO2 ), 0.01 to 0.19 percent sulfur, and 0.004 to 0.82 percent calcium oxide (CaO). Human Health Concerns The primary human health concern associated with graphite mining is inhalation of dust and fumes generated during mining and processing. Graphite is not considered to be toxic and is not a listed carcinogen, although crystalline silica (a common impurity in graphite) is considered to be carcinogenic. Graphite is considered a nuisance dust. The time-weighted average (TWA) recommended exposure level set by the U.S. National Institute for Occupational Safety and Health (NIOSH) is 2.5 milligrams per cubic meter. Chronic exposure to graphite dust is associated with pneumoconiosis, a group of lung diseases associated with chronic exposure to mineral and metallic dusts. Graphite pneumoconiosis was recognized in the 1940s in graphite workers in Sri Lanka based on similarities to pneumoconiosis in coal miners (Uragoda, 1997). The fact that graphite always contains some quartz (typically about 2 percent but up to 10 percent) raised concerns that graphite pneumoconiosis was actually a slow developing form of silicosis (Ranasinha and Uragoda, 1972). A review of 605 cases of graphite pneumo­ coniosis reported in the literature and experimental studies on animals concluded that although many years of occupational exposure to pure graphite may cause disease, most studies indicate that mixed-dust inhalation is a more likely cause of lung disease (Hanoa, 1983). Implementation of dust abatement protocols in mining and processing has resulted in decreased incidence of lung disease in graphite workers since the 1970s. Ecological Health Concerns The environmental fate and effects of dispersed graphite flakes were addressed in a study of the use of graphite flakes in a dust cloud to obscure visual and electromagnetic observa­ tion of military operations under battlefield conditions (Driver and others, 1993). Graphite mixed with fog oil and dispersed as an aerosol provides a chemically inert obscurant used to protect movements of troops and equipment. Dispersion of airborne plumes of these mixtures can deposit graphite on soil, vegetation, and water surfaces or pose inhalation risks to wildlife. Although obscurant releases are short-term events (~30 minutes), airborne distribution and surface deposition of flake graphite can occur many kilometers downwind of the release site. Deposited graphite persists in the environment, so the repeated use on military training sites warranted an evaluation of potential ecological impacts. These studies are not directly applicable to graphite mining and processing, but they do demonstrate that graphite flakes likely pose little or no chemical risk to the environment. The series of experiments described by Driver and others (1993) showed that (a) graphite flakes are not toxic to soil invertebrates (oligochaeta, or earth­ worms), (b) no adverse effects on terrestrial plants (corn and cucumber) were noted in soils amended with graphite flakes in

Problems and Future Research    J21 concentrations up to 0.5 percent, by weight, and (c) a 48-hour acute aquatic toxicity test toward daphnia (water fleas) using graphite suspensions was toxic; however, iron contaminants in the graphite may explain the toxicity. The long-term effects of obscurant flake graphite on exposed avian and mammalian wildlife are unknown. Carbon Footprint The term "carbon footprint" refers to the amount of carbon dioxide (CO2 ) emitted in a 1-year period. According to GrafTech International Holdings, Inc. (2013), natural graphite has a substantially lower carbon footprint for both CO2 emissions and energy consumption during mining and processing than other mineral commodities for which data are available, such as aluminum or copper, on an equivalent mass, volume, or yearly production basis. Cost- and energy-efficient technologies that could reduce CO2 to synthetic graphite could lower CO2 emissions and produce inert graphite, providing an industrial option to sequester carbon from the atmosphere (Xu and others, 2005). Regulatory and Environmental Considerations The environmental requirements for natural graphite, which is an inert, nontoxic substance, are limited to dust control and control of organic vapors that may arise during mining or processing of graphite ores or the fabrication of graphite products. Given the current and likely future absence of graphite mining in the United States, no other domestic regulatory or environmental requirements are anticipated. Problems and Future Research Major shifts in U.S. consumption of natural graphite by end use are underway and include a long-term decrease in the use of amorphous graphite for refractory and other applica­ tions and an increase in the use of flake graphite, particularly for emerging energy and high-technology applications (Taylor, 2006). In addition, shifts in the global graphite supply and exports are anticipated as China's rapidly growing domestic market for graphite, coupled with their developing mine production problems and rising labor costs, may serve to limit Chinese exports in the future, particularly of crystalline flake graphite; meanwhile, anticipated large-scale fuel cell and battery applications could dramatically increase world demand for graphite (Taylor, 2006; Olson, 2013; Olson and others, 2016). For the near future, however, China's graphite production is expected to increase and its dominance of world production to continue (Olson, 2013). Possible disruptions to global supplies are likely to be temporary or sporadic because identified reserves in China are sufficient to support new mines and additional production. In addition, exploration for new flake graphite deposits is ongoing, and additional deposits are near development in Canada and elsewhere (Olson, 2013; Olson and others, 2016). Other than scientific studies on some vein graphite deposits of scientific (not commercial) interest, little recent geologic characterization and study has been undertaken on graphite deposits in the United States, and exploration for new deposits has not taken place. The lack of exploration is chiefly because known deposits are considered noncommercial, large areas of the country lack the geologic conditions and settings thought necessary to form economic graphite deposits, graphite supplies have been reliably available from foreign sources for many years, and synthetic graphite is increasingly used for many applications. As earlier noted by Weis (1973), research and development of better techniques to beneficiate low-grade flake graphite ores would be needed to support a viable domestic industry. Studies on the temporal variation of carbon deposition and preservation and the behavior of organic matter and graphite under metamorphic and hydrothermal conditions might provide additional insights into the occurrence and distribution of high-grade flake graphite deposits. Many of the important flake graphite deposits worldwide occur in Precambrian crystalline metamorphic rocks, and most of these occur in Pan-African age supracrustal metamorphic belts. In addition, many of these deposits have grades exceeding 15 percent contained carbon, which exceeds the typical carbon content range of organic-bearing shales (Vine and Tourtelot, 1970). It is not known whether these deposits represent unusual protoliths—for example, saprolitic alginate (oilshale), unusual periods or regions of biological productivity and preservation of organic matter, or if they record some carbon enrichment owing to mechanical deformation or precipitation of graphite by processes involving internal or external buffering or mixing of metamorphic fluids.

J22    Critical Mineral Resources of the United States — Graphite References Cited Note: All Web links listed were active as of the access date but may no longer be available. Alling, H.L., 1918, The Adirondack graphite deposits: Albany, N.Y., New York State Museum Bulletin 199, 172 p. Bastin, E.S., 1912, The graphite deposits of Ceylon, with a description of a similar graphite deposit near Dillon, Montana: Economic Geology, v. 7, p. 419-443. Bonneau, J., and Raby, R., 1990, The Lake Knife graphite deposit: Mining Magazine, v. 163, no. 1, p. 12-18. Chacko, T., Kumar, G.R.R., and Newton, R.C., 1987, Metamorphic P-T conditions of the Kerala (South India) khondalite belt, a granulite facies supracrustal terrain: The Journal of Geology, v. 95, no. 3, p. 343-358. Chamberlain, C.P., and Rumble, D., 1988, Thermal anomalies in a regional metamorphic terrain—An isotopic study of the role of fluids: Journal of Petrology, v. 29, p. 1215-1232. Chorlton, L.B., 2007, Generalized geology of the world— Bedrock domains and major faults in GIS format; a smallscale world geology map with an extended geological attribute database: Geological Survey of Canada Open File 5529, 48 p., CD-ROM. Coats, R.R., 1944, Graphite deposits on the north side of the Kigluaik Mountains, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 10, 8 p. Driver, C.J., Ligotke, M.W., Landis, W.G., Downs, J.L., Tiller, B.L., Moore, E.B., Jr., and Cataldo, D.A., 1993, Environmental and health effects review for obscurant graphite flakes—Report prepared for the U.S. Army Chemical and Biological Defense Agency: Richland, Wash., Pacific Northwest Laboratory, 28 p. European Commission, 2014, Critical raw materials for the EU— Report of the ad-hoc Working Group on defining critical raw materials: Brussels, Belgium, and Luxembourg, Luxembourg, European Commission, 41 p., accessed September 19, 2015, at ://ec.europa.eu/growth/sectors/raw-materials/ specific-interest/critical/index_en.htm. Ford, R.B., 1954, Occurrence and origin of the graphite deposits near Dillon, Montana: Economic Geology, v. 49, p. 31-43. Goosens, P.J., 1982, Graphite deposits of the Precambrian and their mining development, in Natural Resources and Energy Division, United Nations Department of Technical Cooperation for Development, The development poten­ tial of Precambrian mineral deposits: New York, N.Y., Pergamon Press, p. 123-155. GrafTech International Holdings, Inc., 2013, About natural graphite: GrafTech International Holdings, Inc., accessed September 19, 2015, at ://aetpublic.wiredviews.com/ getdoc/411491a4-0d68-4781-993e-7d992adfa2d4/TradeShows.aspx. Hanoa, Rolf, 1983, Graphite pneumoconiosis—A review of etiologic and epidemiologic aspects: Scandinavian Journal of Work, Environment, and Health, v. 9, no. 4, p. 303-314. Hoefs, J., and Frey, M., 1976, The isotopic composition of carbonaceous matter in a metamorphic profile from the Swiss Alps: Geochimica et Cosmochimica Acta, v. 40, p. 945-951. Industrial Minerals, 2010, Graphite prices rising daily: Industrial Minerals, June 29, accessed September 15, 2019, at ://www.indmin.com/Article/2620429/Graphite-pricesrising-daily.. Jambor, J.L., 2003, Mine-waste mineralogy and mineralogical perspectives of acid-base accounting, chap. 6 of Jambor, J.L., Blowes, D.W., and Ritchie, A.I.M., eds., Environmental aspects of mine wastes: Mineralogical Association of Canada Short Course Series, v. 31, p. 117-145. Klar, G., 1958, The important graphite deposits of the world: Mining Magazine, v. 98, p. 137-142. Krauss, U.H., Schmidt, H.W., Taylor, H.A., Jr., and Sutphin, D.M., 1988, International Strategic Minerals Inventory summary report—Natural graphite: U.S. Geological Survey Circular 930-H, 29 p. [Also available at ://pubs.er.usgs.gov/ publication/cir930H.] Kuehnbaum, R., and Zebruck, G., 2002, Treelined Lake graphite deposit—Beneficiation study: Megagraphite Inc. Treelined Lake Project report, 10 p. plus details of tests, accessed September 19, 2015, at :// www.geologyontario..gov.on.ca/mndmfiles/afri/ data/imaging/52L08SW2010//52L08SW2010.Pdf. Lamb, W., and Valley, J.W., 1984, Metamorphism of reduced granulites in low-CO2 vapor free environment: Nature (London), v. 312, November 1, p. 56 -58. [Also available at ://dx.doi.org/10.1038/312056a0.] Landis, C.A., 1971, Graphitization of dispersed carbonaceous material in metamorphic rocks: Contributions to Mineralogy and Petrology, v. 30, p. 34-45. Li, C., Yue, J., and Zhang, Y., 1985, Research on geological background and origin of Liu Mao graphite deposits, Heilongjiang Province, in Cheng, Y., ed., International Symposium on Metallogeny of the Early Precambrian: Abstracts, Organizational Committee of the International Symposium of Metallogeny, China, p. 108-109. Liu, Wen-yong, and Man, Xiu-liu, 2007, Evaluation and content of heavy metal pollution in mine areas wasteland of Jixi: Journal of Soil and Water Conservation, v. 6, p. 70-74.

References Cited    J23 Natural Earth, 2014, Small scale data: Natural Earth map dataset, scale 1:110,000,000, accessed February 12, 2014, at ://www.naturalearthdata.com/. Needham, A.B., 1946, Mining and milling operations of Southwestern Graphite Co., Burnet County, Texas: U.S. Bureau of Mines Information Circular 7339, 7 p. Newton, R.C., 1986, Fluids of granulite facies metamorphism, in Walther, J.V., and Wood, B.J., eds., Fluid-rock interac­ tions during metamorphism: Berlin, Springer, p. 36-59. O'Driscoll, Mike, 2010, Minerals meet in Miami heat: Industrial Minerals, no. 510, February 25, accessed September 19, 2015, at ://www.indmin.com/ Article/2398524/Minerals-meet-in-Miami-heat./. Olson, D.W., 2011, Graphite (natural): U.S. Geological Survey Mineral Commodity Summaries 2011, p. 68-69, accessed February 25, 2013, at ://minerals.usgs.gov/minerals/ pubs/commodity/graphite/mcs-2011-graph.pdf. Olson, D.W., 2012, Graphite, in Metals and minerals: U.S. Geological Survey Minerals Yearbook 2010, v. I, p. 32.1-32.10, accessed November 12, 2012, at ://minerals.usgs.gov/minerals/pubs/commodity/ graphite/myb1-2010-graph.pdf. Olson, D.W., 2013, Graphite (natural): U.S. Geological Survey Mineral Commodity Summaries 2013, p. 68-69, accessed February 25, 2013, at ://minerals.usgs.gov/minerals/ pubs/commodity/graphite/mcs-2013-graph.pdf. Olson, D.W., Virta, R.L., Mahdavi, Mahbood, Sangine, E.S., and Fortier, S.M., 2016, Natural graphite demand and supply—Implications for electric vehicle battery require­ ments, in Wessel, G.R., and Greenberg, J.K., eds., Geoscience for the public good and global development— Toward a sustainable future: Geological Society of America Special Paper 520, p. SPE520-08, April 19, accessed June 30, 2016, at Pallister, H.D., and Thoenin, J.R., 1948, Flake graphite and vanadium investigations in Clay, Coosa, and Chilton Counties, Alabama: U.S. Bureau of Mines Report of Investigations 4366, 81 p. Ranasinha, K.W., and Uragoda, G.G., 1972, Graphite pneu­ moconiosis: British Journal of Industrial Medicine, v. 29, p. 178-183. Roskill Information Services, Ltd., 2012, Natural and synthetic graphite—Global industry markets and outlook, 8th ed.: London, Roskill Information Services, Ltd., 413 p. Rumble, D., III, and Hoering, T.C., 1986, Carbon isotope geochemistry of graphite vein deposits from New Hampshire, U.S.A.: Geochimica et Cosmochimica Acta, v. 50, no. 6, p. 1239-1247. Rumble, D., III, Duke, E.F., and Hoering, T.C., 1986, Hydrothermal graphite in New Hampshire—Evidence of carbon mobility during regional metamorphism: Geology, v. 14, no. 6, p. 452-455. 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J24    Critical Mineral Resources of the United States — Graphite Uragoda, C.G., 1997, A cohort study of graphite workers in Sri Lanka: Occupational Medicine, v. 47, no. 5, p. 269-272. U.S. Geological Survey, 1996, Global 30 arc-second elevation (GTOPO30): Reston, Va., U.S Geological Survey dataset (digital elevation model), accessed February 12, 2014, at ://lta.cr.usgs.gov/GTOPO30. U.S. Geological Survey, 2012, Mineral Resources Data System: U.S. Geological Survey database, accessed April 4, 2012, at ://mrdata.usgs.gov//. Vine, J.D., and Tourtelot, E.B., 1970, Geochemistry of black shale deposits—A summary report: Economic Geology, v. 65, p. 253-272. Weis, P.L., 1973, Graphite, in Brobst, D.A., and Pratt, W.P., eds., United States mineral resources: U.S. Geological Survey Professional Paper 820, p. 277-283. [Also available at ://pubs.er.usgs.gov/publication/pp820.] Wilde, S.A., Dorsett-Bain, H.L., and Lennon, R.G., 1999, Geological setting and controls on the development of graphite, sillimanite and phosphate mineralization within the Jiasmusi Massif—An exotic fragment of Gondwanaland located in north-eastern China?: Gondwana Research, v. 2, no. 1, p. 21-46. Xu, A., Indala, S., Hertwig, T.A., Pike, R.W., Knopf, F.C., Yaws, C.L., and Hopper, J.R., 2005, Development and integration of new processes consuming carbon dioxide in multi-plant chemical production complexes: Clean Technology Environmental Policy, v. 7, p. 97-115. Zavalyevskiy Graphite Ltd., 2013, Home page: Zavalyevskiy Graphite Ltd. Web site, accessed September 19, 2015, at ://zvgraphit.com.ua/en/. Zeitler, P.K., Barreiro, B., Chamberlain, C.P., and Rumble, D., III, 1990, Ion-microprobe dating of zircon from quartz-graphite veins at the Bristol, New Hampshire, metamorphic hot spot: Geology, v. 18, p. 626-629.

For more information concerning this report, please contact: Mineral Resources Program Coordinator U.S. Geological Survey 913 National Center Reston, VA 20192 Telephone: 703- 648- 6100 Fax: 703- 648- 6057 Email: minerals@usgs.gov Home page: ://minerals.usgs.gov Prepared by the USGS Science Publishing Network Reston Publishing Service Center Edited by J.C. Ishee Illustrations by Caryl J. Wipperfurth Layout by Caryl J. Wipperfurth and Cathy Y. Knutson Posting by Angela E. Hall

Robinson, Jr., and others—Critical Mineral Resources of the United States—Graphite—Professional Paper 1802-J ISSN 2330-7102 (online) ://doi.org/10.3133/pp1802J