Graphite Introduction, Classification, Application, Demand and Availability of Supply, Geology, Resources and Production


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 suitable 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 a 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 the 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 non-toxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dust, 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 the 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 in 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 to Graphite

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, graphene, 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 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 manufactured 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. 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 by Klar (1958), Weis (1973), Krauss and others (1988), and Taylor (2006).

Descriptive models of the geology and characteristics 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 accumulations 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

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 which 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 is disseminated in beds of carbonaceous sediments 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 predominately Archean to late Proterozoic in age. 

c. “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 the 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 into 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 non-metallic 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.

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 high-temperature 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.

Fine-grained microcrystalline graphite powder (amorphous 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 anti-corrosion products, batteries, carbon brushes, coatings, conductive fillers, electrodes 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 applications 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).


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 is 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 tend 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, diamonds, 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, planar honeycomb-lattice sheets. When the graphite structure is only a 1-atom-thick planar sheet, it is called graphene.

Deposit Types

Natural graphite is a common constituent of metasedimentary 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 depends on its location and transportation costs to markets in addition to deposit grade, size, and mining characteristics. 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 the 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 organic-rich 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.

Thermal metamorphism is commonly caused by crosscutting diabasic or granitic intrusions with associated hornfels alteration of host rocks. Hornfels is a hard metamorphic rock formed by contact metamorphism of sedimentary rocks close to intrusive igneous bodies.

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 the 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 conditions (amphibolite facies). 

These metamorphic conditions are sufficient to crystallize fully ordered graphite 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 the 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 basements; their worldwide distribution has been mapped by Chorlton (2007). Most flake graphite deposits are located in the Precambrian crystalline metamorphic basement (fig. J2), principally of Neoarchean to Proterozoic eras; however, deposits could occur in the 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, segregations within fold crests, and 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. 

Crystals in each deposit vary from a fraction of a millimeter 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.

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 exception 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.

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 the worldwide production 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.

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 coalfields 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 the 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.

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 resolutions 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 presence 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 sediments 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. 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. 

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. 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 [V2 O5 ]), titanium (0.5 percent titanium dioxide [TiO2]), and uranium (0.004 percent U).

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 applications and an increase in the use of flake graphite, particularly for emerging energy and high-technology applications

. 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. In the near future, however, China’s graphite production is expected to increase and its dominance of world production to continue. 

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. 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 (oil-shale), 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.

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