References

Strategic Materials

The US is heavily reliant on imports of certain mineral commodities that are vital to the nation's security and economic prosperity. This dependency of the US on foreign sources creates a strategic vulnerability - for both its economy and military - to adverse foreign government action, natural disaster, and other events that can disrupt supply of these key minerals.

The Strategic and Critical Materials Stock Piling Act, first enacted in 1939 and most recently amended in 1979, provides for the acquisition and retention of stocks of certain strategic and critical materials to decrease and preclude dependence upon foreign sources or single points of failure for strategic materials in times of national emergency. Such materials when acquired and stored constitute and are collectively known as the National Defense Stockpile.

In 2018, the Secretary of Interior published a list of 35 mineral commodities deemed "critical" under the definition provided in an Executive Order 13817, dated 20 December 2017.

Both the National Defense Stockpile list of materials and the Department of Interior 2018 list serve as the basis of this appendix. The materials tabulated here can also be found under the natural resources and economic entries for individual countries; they are consolidated below for the convenience of the reader. This listing includes those materials deemed essential for the production of critical items such as aircraft and aircraft engines, ammunition, electronics and telecommunications, sensors, and specialty steels.
 
Each entry below includes the name of the material with its chemical symbol and atomic number (for metals, precious metals, non-metals, and rare earth elements), or chemical composition (for compounds), a description, a list of uses, import sources to the US, world resources, and any available substitutes.

The appendix is subdivided into Compounds, Metals, Non-Metals, and Rare Earth Elements; these can be accessed by clicking on C, M, N, or R respectively.

The terms element, mineral, noble metal, ore, and compound appear under various materials entries. An element is a fundamental substance that cannot be broken down chemically and consists of atoms of only one kind (all of the metals and rare earths listed in this appendix are elements). Minerals are inorganic solids that have a characteristic chemical composition (are composed of several elements) and with a specific crystalline structure (e.g., sphalerite - a mineral composed of the elements zinc and sulfur). Ores are concentrations of minerals in rock that are high enough to be economically extracted for use (e.g., bauxite ore is the main source of aluminum). Noble metals are elements that resist corrosion and oxidation (e.g., platinum). Compounds are chemical substances composed of a particular set of two or more different elements combined into one substance through a chemical reaction (e.g., barite - a compound combining barium, sulfur, and oxygen created through geologic processes).

Information in this appendix is derived from the Department of Defense and the Department of the Interior.

Compounds

Barite or Barium Sulfate (BaSO4)

Description: Barite, a name that was derived from the Greek word "barus" (heavy), is the mineralogical name for barium sulfate. In commerce, the mineral is sometimes referred to as "baryte." 

Uses: used as a filler, extender, or weighting agent in products such as paints, plastics, and rubber; some specific applications include use in automobile brake and clutch pads, automobile paint primer for metal protection and gloss, used as a weighting agent in rubber, and in cement jackets around underwater petroleum pipelines; in the metal-casting industry, molds are often coated with barium sulfate to prevent the molten metal from bonding with the mold; because barite significantly blocks x-ray and gamma-ray emissions, it is used as aggregate in high-density concrete for radiation shielding around x-ray units in hospitals, nuclear power plants, and university nuclear research facilities; ultrapure barite is used as a contrast medium in x-ray and computed tomography examinations of the gastrointestinal tract

US imports: 2,600,000 mt (2019 est.)

Import Sources (2015–18): China, 58%; India, 17%; Morocco, 12%; Mexico, 11%; and other, 2%

World Resources: In the US, identified resources of barite are estimated to be 150 million tons, and undiscovered resources contribute an additional 150 million tons. The world’s barite resources in all categories are about 2 billion tons, but only about 740 million tons are identified resources. However, no known systematic assessment of either US or global barite resources has been conducted since the 1980s.

Substitutes: In the drilling mud market, alternatives to barite include celestite, ilmenite, iron ore, and synthetic hematite that is manufactured in Germany. None of these substitutes, however, has had a major impact on the barite drilling mud industry.

Note(s): More than 90% of the barite sold in the US is used as a weighting agent in fluids used in the drilling of oil and natural gas wells.

Fluorspar or Calcium Fluoride (CaF2)

Description: When found in nature, fluorspar is known by the mineral name fluorite. Fluorspar is calcium fluoride (CaF2). Metallurgical grade fluorspar (60–85% CaF2), is traditionally used as a flux to lower the melting point of raw materials in steel production to facilitate the removal of impurities, and in the production of aluminum. Ceramic grade fluorspar (85–95% CaF2) is used in the manufacture of enamels. Acid grade fluorspar (97%+ CaF2) is used to make hydrogen fluoride and hydrofluoric acid.

Uses: metal processing; steel and iron production; catalyst; semiconductor etching; electrical power distribution; pharmaceuticals; high-quality camera and telescope lenses; seals and adhesives in engine components

US imports: 440,000 mt (2019 est.) The US is 100% import reliant for its fluorspar needs.

Import Sources (2015–18): Mexico, 66%; Vietnam, 13%; South Africa, 8%; China, 6%; and other, 7%.

World Resources: No known systematic assessment of either US or global resources has been conducted since the 1980s. Enormous quantities of fluorine are present in phosphate rock. Current US reserves of phosphate rock are estimated to be 1 billion tons, containing about 72 million tons of 100% fluorspar equivalent assuming an average fluorine content of 3.5% in the phosphate rock. World reserves of phosphate rock are estimated to be 70 billion tons, equivalent to about 5 billion tons of 100% fluorspar equivalent.

Substitutes: Fluorosilicic acid is used to produce aluminum fluoride (AlF3), but because of differing physical properties, AlF3 produced from fluorosilicic acid is not readily substituted for AlF3 produced from fluorspar. Fluorosilicic acid has been used to produce hydrofluoric acid, but this practice has not been widely adopted. However, the preferred product is currently aqueous hydrofluoric acid rather than fluorspar. Aluminum smelting dross, borax, calcium chloride, iron oxides, manganese ore, silica sand, and titanium dioxide have been used as substitutes for fluorspar fluxes.

Note(s): Hydrofluoric acid is the primary feedstock for the manufacture of virtually all fluorine-bearing chemicals and is also a key ingredient in the processing of aluminum and uranium. Fluorspar is also used in cement production, in enamels, as a flux in steelmaking, in glass manufacture, in iron and steel casting, and in welding rod coatings. A new mine in Canada that began operation in late 2017 reportedly sent its first shipment of 4,700 tons of fluorspar to the US. Another new mine in South Africa was under construction and production was expected to begin in early 2019.

Potash (potassium-containing compounds such as KCl)

Description: Potash denotes a variety of mined and manufactured salts that contain the element potassium in water-soluble form.

Uses: The fertilizer industry uses about 85% of US potash, and the remainder is used for chemical and industrial applications. About 65% of the potash produced is potassium magnesium sulfate (K2Mg2(SO4)3) and potassium sulfate (K2SO4), which are required to fertilize certain chloride sensitive crops. Muriate of potash (KCl) accounted for the remaining 35% of production and is used for agricultural and chemical applications.

US Imports: 5 million mt (2019 est.)

Import Sources (2015–18): Canada, 81%; Russia, 8%; Belarus, 5%; Israel, 2%; and other, 4%

World Resources: Estimated US domestic potash resources total about 7 billion tons. Estimated world resources total about 250 billion tons.

Substitutes: No substitutes exist for potassium as an essential plant nutrient and as an essential nutritional requirement for animals and humans. Manure and glauconite (greensand) are low-potassium-content sources that can be profitably transported only short distances to crop fields.

Metals

Aluminum (Al/13)

Description: Aluminum or aluminium is a silver-white metal, very light in weight (less than three times as dense as water), yet relatively strong. Because aluminum is ductile, it can be drawn into wires or pressed into sheets or foil. It is the most abundant metallic element, and the third most abundant of all elements in the Earth's crust, making up 8% of the crust by weight. Only silicon and oxygen are more plentiful. Bauxite ore is the main source of aluminum; bauxite is processed into alumina before being processed into metallic applications.

Uses: transportation; containers and packaging; building and construction; electrical; machinery and equipment; structural airframe material for aircraft; military and combat vehicles

US Imports: 7.2 million mt (2019 est.)

Import Sources (2015–18): Bauxite: Jamaica 51%, Brazil 23%, Guinea 10%, Guyana 7%, other 9%; Alumina: Brazil 39%, Australia 31%, Jamaica 9%, Canada 5%, other 16%

World Resources: Global resources of bauxite are estimated to be between 55 to 75 billion tons and are sufficient to meet world demand for metal well into the future.

Substitutions: Composites can substitute for aluminum in aircraft fuselages and wings. Glass, paper, plastics, and steel can substitute for aluminum in packaging. Composites, magnesium, steel, and titanium can substitute for aluminum in ground transportation uses. Composites, steel, vinyl, and wood can substitute for aluminum in construction. Copper can replace aluminum in electrical and heat-exchange applications.

Antimony (Sb/51)

Description: Antimony is a silvery-gray, brittle semi-metal. It rarely occurs in nature as a native element, but is found in a number of different minerals, the most important of which is stibnite. Antimony is often called a semi-metal because in pure form it is not shiny and malleable like true metals.

Uses: automotive batteries (lead-acid); ceramics and glass; flame retardants (flameproof fabrics); automotive brake pads (additive to adjust co-efficient of friction); cable sheathing

US Imports: 24,340 mt (2019 est)

Import Sources (2015–18): Metal: China 52%, India 20%, Vietnam 8%, United Kingdom 6%, other 14%; Ore and concentrate: Italy 76%, China 17%, Mexico 4%, Bosnia and Herzegovina 1%, other 2%; Oxide: China 64%, Belgium 10%, Thailand 10%, Bolivia 7%, other 9%

World Resources: Principal identified world resources are in Australia, Bolivia, China, Mexico, Russia, South Africa, and Tajikistan.

Substitutions: Selected organic compounds and hydrated aluminum oxide are substitutes as flame retardants. Chromium, tin, titanium, zinc, and zirconium compounds substitute for antimony chemicals in enamels, paint, and pigments. Combinations of calcium, copper, selenium, sulfur, and tin are substitutes for alloys in lead-acid batteries.

Note(s): US resources of antimony are mainly in Alaska, Idaho, Montana, and Nevada.

Beryllium (Be/4)

Description: Beryllium is the 44th most abundant element in the earth’s crust. Beryllium is a silvery-white, hard and brittle, extremely light metal, which is highly toxic. The mechanical and thermal properties relating to its low density are superior to those of all other materials, making it very useful for structural and electronic applications. Beryllium metal can be vacuum cast as an ingot or hot pressed as a powder.

Uses: battery contacts and electronic connectors; windows for X-ray tubes; aerospace castings; high-definition and cable television; underwater fiber-optic cable systems; high-density circuits for high-speed computers and automotive ignition systems; pacemakers and other medical devices

US Imports: 45 mt (2019 est.)

Import Sources (2015–18): Kazakhstan, 39%; Japan, 15%; Brazil, 13%; United Kingdom, 5%; and other, 28%

World Resources: The world’s identified resources of beryllium have been estimated to be more than 100,000 tons. About 60% of these resources are in the US; by size, the Spor Mountain area in Utah, the McCullough Butte area in Nevada, the Black Hills area in South Dakota, the Sierra Blanca area in Texas, the Seward Peninsula in Alaska, and the Gold Hill area in Utah account for most of the total.

Substitutes: Because the cost of beryllium is high compared with that of other materials, it is used in applications in which its properties are crucial. In some applications, certain metal matrix or organic composites, high-strength grades of aluminum, pyrolytic graphite, silicon carbide, steel, or titanium may be substituted for beryllium metal or beryllium composites. Copper alloys containing nickel and silicon, tin, titanium, or other alloying elements or phosphor bronze alloys (copper-tin-phosphorus) may be substituted for beryllium-copper alloys, but these substitutions can result in substantially reduced performance. Aluminum nitride or boron nitride may be substituted for beryllium oxide.

Note(s): Apparent consumption of beryllium-based products was estimated to have increased by about 10% in 2017 from that of 2016.

Bismuth (Bi/83)

Description: Bismuth is a silvery-white metallic element with a pinkish tint. Bismuth was long thought to be a variety of lead or tin, which it resembles, until the chemist Claude Geoffroy showed in 1753 that it is a separate element.

Uses: cosmetics (bismuth oxychloride); pharmaceuticals (compounds used in over-the-counter to treat stomach illness, burns, intestinal disorders, and stomach ulcers); metal alloys; solder; thermoelectric devices (bismuth telluride); fireworks; plastics with opacity to X-rays (implanted medical devices); ammunition (replacement for lead shot used for hunting, "less-lethal" riot projectile)

US Imports: 2,400 mt (2019 est.)

Import Sources (2015–18): China, 76%; Belgium, 6%; Mexico, 6%; Republic of Korea, 5%; and other, 7%

World Resources: World reserves of bismuth are usually estimated based on the bismuth content of lead resources because bismuth production is most often a byproduct of processing lead ores. In China and Vietnam, bismuth production is a byproduct or coproduct of tungsten and other metal ore processing.

Substitutes: Bismuth compounds can be replaced in pharmaceutical applications by alumina, antibiotics, and magnesia. Titanium dioxide-coated mica flakes and fish-scale extracts are substitutes in pigment uses. Indium can replace bismuth in low-temperature solders. Resins can replace bismuth alloys for holding metal shapes during machining, and glycerine-filled glass bulbs can replace bismuth alloys in triggering devices for fire sprinklers. Free machining alloys can contain lead, selenium, or tellurium as a replacement for bismuth.

Note(s): Bismuth, at an estimated 8 parts per billion by weight, ranks 69th in elemental abundance in the Earth’s crust and is about twice as abundant as gold. Bismuth minerals rarely occur in sufficient quantities to be mined as principal products; a mine in China is the only one where bismuth is the primary product.

Cadmium (Cd/48)

Description: Cadmium is a very soft, silvery-white metallic element; it is so soft that it can be cut with a knife. Cadmium has many chemical similarities to zinc, but is less reactive with acids than is zinc. Metallic cadmium is rarely used industrially in pure form.

Uses: nickel cadmium (NiCd) batteries; pigments (yellow, orange, and red); plating (provides better rust resistance than zinc, especially in salt water environments)

US Imports: 440 mt (2019 est.)

Import Sources (2015–18): China, 25%; Australia, 22%; Canada, 21%; Peru, 10%; and other, 22%.

World Resources: Most of the world’s primary cadmium metal is produced in Asia, and leading global producers are China, the Republic of Korea, and Japan. A smaller amount of secondary cadmium metal is recovered from recycling NiCd batteries.

Substitutes: Lithium-ion and nickel-metal hydride batteries can replace NiCd batteries in many applications. Except where the surface characteristics of a coating are critical (for example, fasteners for aircraft), coatings of zinc, zinc-nickel, or vapor-deposited aluminum can be substituted for cadmium in many plating applications. Cerium sulfide is used as a replacement for cadmium pigments, mostly in plastics. Barium-zinc or calcium-zinc stabilizers can replace barium-cadmium stabilizers in flexible PVC applications. Amorphous silicon and copper-indium-gallium-selenide photovoltaic cells compete with cadmium telluride in the thin-film solar-cell market.

Note(s): Cadmium is generally recovered from zinc ores and concentrates. Sphalerite, the most economically significant zinc ore mineral, commonly contains minor amounts of cadmium, which shares certain similar chemical properties with zinc and often substitutes for zinc in the sphalerite crystal lattice. The cadmium mineral greenockite is frequently associated with weathered sphalerite and wurtzite.

Cesium (Cs/55)

Description: Cesium is a very soft, ductile, alkali metal that is liquid at 28.4° C. It is the most electropositive and reactive of the alkali metals and forms compounds with a variety of anions and alloys with the other alkali metals and with gold. The metal ignites spontaneously in the presence of air and reacts explosively in water. Because of this reactivity, cesium is classed as a hazardous material and must be stored and transported in isolation from possible reactants.

Uses: The current application that likely requires the most cesium is as a specialty high-density component in drilling mud used for petroleum exploration. Cesium also has a wide-spectrum of photoemissive properties whereby electromagnetic radiation, which includes visible light and nearby regions of the radiation spectrum, are converted to electrical current. Thus, cesium is used in television image devices, night-vision equipment, solar photovoltaic cells, and other types of photoelectric cells. Perhaps one of its best known applications is its use in the super-accurate atomic cesium clock that is used as a standard for the world’s timekeeping systems. It is also used in the chemical process industry, primarily as an ingredient of metal-ion catalysts; in medical applications; in the removal of sulfur from crude oil in petroleum refining; and as an ingredient in specialty glasses used in fiber optics and night-vision devices.

US imports: Only a few thousand kilograms of cesium are consumed in the US every year. The US is 100% import reliant for its cesium needs.

Import Sources (2014–17): No reliable data has been available to determine the source of cesium ore imported by the US since 1988. Previously, Canada was thought to be the primary supplier of cesium ore.

World Resources: US and world resources of cesium have not been estimated. It is a relatively uncommon element that can be mined in only a few places in the world. The world’s largest deposit of pollucite, which is the principal ore of cesium, is in a zoned pegmatite at Bernic Lake, Canada, and accounts for more than two-thirds of world reserves. Other reserves are in Namibia and Zambia, although numerous low-grade occurrences are known to exist elsewhere. There are cesium occurrences in pegmatite in Afghanistan, China, and Italy, in hydrous opal in Tibet, and in brines in Chile.

Substitutes: Cesium and rubidium can be used interchangeably in many applications because they have similar physical properties and atomic radii. Cesium, however, is more electropositive than rubidium, making it a preferred material for some applications. However, rubidium is mined from similar deposits, in relatively smaller quantities, as a byproduct of cesium production in pegmatites and as a byproduct of lithium production from lepidolite (hard-rock) mining and processing, making it no more readily available than cesium.

Note(s): During 2018, projects that were primarily aimed at developing lithium resources with cesium content were at various stages of development, including eight subprojects at the King Col project in Australia, the Jubilee Lake lithium prospect in Canada, the Soris lithium project in Namibia, and the Winnipeg River pegmatite field in Canada. The status of these projects ranged from early feasibility studies to active exploration and drilling. No production has been reported at any sites.

Chromium (Cr/24)

Description: Chromium is a steely-gray, lustrous, hard and brittle metal that takes a high polish, resists tarnishing, and has a high melting point. Chromium is produced from chromite ore. About 80% of world production of chromite ore comes from India, Kazakhstan, and South Africa.

Uses: component in nickel super-alloys for land based turbines and jet engines; component in high-speed tool steel; surface coatings; catalysts for processing hydrocarbons; refractory materials; resistance heating wires

US Imports: 520,000 mt (2019 est.)

Import Sources (2015–18): Chromite (mineral): South Africa, 99%; and Canada, 1%. Chromium containing scrap: Canada, 49%; Mexico, 43%; and other, 8%. Chromium (primary metal): South Africa, 34%; Kazakhstan, 9%; Russia, 8%; and other, 49%. Total imports: South Africa, 38%; Kazakhstan, 7%; Russia, 6%; and other, 49%.

World Resources: World resources are greater than 12 billion tons of shipping-grade chromite, sufficient to meet conceivable demand for centuries. The world’s chromium resources are heavily geographically concentrated (95%) in Kazakhstan and southern Africa; US chromium resources are mostly in the Stillwater Complex in Montana.

Substitutes: Chromium has no substitute in stainless steel, the leading end use, or in superalloys, the major strategic end use. Chromium-containing scrap can substitute for ferrochromium in some metallurgical uses.

Note(s): Stainless steels and superalloys require chromium. In 2019, the United States was expected to consume 4% of world chromite ore production in various forms of imported materials, such as chromite ore, chromium chemicals, chromium ferroalloys, chromium metal, and stainless steel.

Cobalt (Co/27)

Description: Cobalt is a bluish-gray, shiny, brittle metallic element. It has magnetic properties like iron. Cobalt-nickel alloys have good temperature stability and corrosion and wear resistance and are used in high temperature applications. The cobalt resources identified in the world are mostly found in copper or nickel mines in Australia, Canada, Democratic Republic of the Congo (DROC), Russia, and Zambia. In the US, cobalt resources are in mostly found in Minnesota. Most of the cobalt used in the US is imported.

Uses: batteries; component in nickel superalloys for high temperature sections of jet engines and industrial gas turbines; pigments; medical implants

US Imports: 13,600 mt (2019 est.)

Import Sources (2015–18): Cobalt contained in metal, oxide, and salts: Norway, 17%; Japan, 13%; China, 11%; Canada, 11%; and other, 48%.

World Resources: Identified world terrestrial cobalt resources are about 25 million tons. The vast majority of these resources are in sediment-hosted stratiform copper deposits in DROC and Zambia; nickel-bearing laterite deposits in Australia and nearby island countries, and in Cuba; and magmatic nickel-copper sulfide deposits hosted in mafic and ultramafic rocks in Australia, Canada, Russia, and the US. The DROC continued to be the world’s leading source of mined cobalt, supplying more than one-half of world cobalt mine production. China was the world’s leading producer of refined cobalt and a leading supplier of cobalt imports to the US. Much of China’s production comes from ore and partially refined cobalt imported from DROC; scrap and stocks of cobalt materials also contributed to China’s supply.

Substitutes: In some applications, substitution for cobalt would result in a loss in product performance. Potential substitutes include barium or strontium ferrites, neodymium-iron-boron, or nickel-iron alloys in magnets; cerium, iron, lead, manganese, or vanadium in paints; cobalt-iron-copper or iron-copper in diamond tools; copper-iron-manganese for curing unsaturated polyester resins; iron, iron-cobalt-nickel, nickel, cermets, or ceramics in cutting and wear resistant materials; iron-phosphorous, manganese, nickel-cobalt-aluminum, or nickel-cobalt-manganese in lithium-ion batteries; nickel-based alloys or ceramics in jet engines; nickel in petroleum catalysts; and rhodium in hydroformylation catalysts.

Note(s): More than 120 million tons of cobalt resources have been identified in manganese nodules and crusts on the floor of the Atlantic, Indian, and Pacific Oceans. Most US cobalt supply is comprised of imports and secondary (scrap) materials. The mineral cobaltite (cobalt sulfarsenide) is a valuable source of cobalt.

Copper (Cu/29)

Description: Copper is a mineral and an element. As a mineral, natural copper (also called native copper) is relatively rare. Copper is usually found in nature in association with sulfur. Copper is one of the oldest metals ever used. Because of its properties of high ductility, malleability, conductivity, and resistance to corrosion, copper has become a major industrial metal, ranking third after iron and aluminum in terms of quantities consumed.

Uses: electric wire (motors, electromagnets, integrated circuits); plumbing (tubing, fittings); architectural roofing and features on buildings; alloys (brass, bronze)

US Imports: 685,000 mt (2019 est.)

US Import Sources (2015–18): Copper content of blister and anodes: South Africa, 61%; Finland, 29%; Malaysia, 8%; and other, 2%; Copper content of ore and concentrates: Mexico, 99%; and other, 1%; Copper content of scrap: Canada, 55%; Mexico, 33%; and other, 12%; Refined copper: Chile, 56%; Canada, 26%; Mexico, 11%; and other, 7%; Refined copper accounted for 85% of unmanufactured copper imports.

World Resources: A 2014 US Geological Survey (USGS) global assessment of copper deposits indicated that identified resources contained about 2.1 billion tons of copper (porphyry deposits accounted for 1.8 billion tons of those resources), and undiscovered resources contained an estimated 3.5 billion tons. A 1998 USGS assessment estimated that 550 million tons of copper were contained in identified and undiscovered resources in the US.

Substitutes: Aluminum substitutes for copper in power cable, electrical equipment, automobile radiators, and cooling and refrigeration tubes. Titanium and steel are used in heat exchangers. Optical fiber substitutes for copper in telecommunications applications, and plastics substitute for copper in water pipe, drain pipe, and plumbing fixtures.   

Gallium (Ga/31)

Description: Gallium is a metallic element that does not easily combine with other elements or ions to form ore minerals. It is, however, found as a trace element in a number of minerals and ores, the most important of which is bauxite (aluminum ore). In fact, gallium is a byproduct of alumina production. Gallium is not produced in the US, and demand is satisfied by imports. More than 95% of gallium consumed in the US is in the form of gallium arsenide.

Uses: integrated circuits (cell phones, especially smart phones, wireless internet); optoelectronic devices (laser diodes, LEDs, photo-detectors, and solar cells); specialty alloys

US Imports: 343 mt (2019 est.). The US is 100% import reliant for its gallium needs.

US Import Sources (2015–18): China, 50%; United Kingdom, 18%; Germany, 10%; Ukraine, 9%; and other, 13%.

World Resources: Globally, primary gallium is recovered as a byproduct of processing bauxite and zinc ores. Gallium contained in world resources of bauxite is estimated to exceed 1 million tons, and a considerable quantity could be contained in world zinc resources. However, less than 10% of the gallium in bauxite and zinc resources is potentially recoverable.

Substitutes: Liquid crystals made from organic compounds are used in visual displays as substitutes for LEDs. Silicon-based complementary metal-oxide semiconductor power amplifiers compete with GaAs power amplifiers in midtier 3G cellular handsets. Indium phosphide components can be substituted for GaAs-based infrared laser diodes in some specific-wavelength applications, and helium-neon lasers compete with GaAs in visible laser diode applications. Silicon is the principal competitor with GaAs in solar-cell applications. GaAs-based ICs are used in many defense-related applications because of their unique properties, and no effective substitutes exist for GaAs in these applications. GaAs in heterojunction bipolar transistors is being replaced in some applications by silicon-germanium.

Note(s): No US primary (low-grade, unrefined) gallium has been recovered since 1987.

Hafnium (Hf/72)

Description: Hafnium metal is produced when it is separated from zircon, a zirconium silicate mineral that is usually 98% zirconium and 2% hafnium. Hafnium is a metallic element used in a number of industrial applications because of its resistance to corrosion and high temperatures.

Uses: control rods on nuclear reactors (primary use); nickel superalloys and high temperature alloys; integrated circuit production for features at 45mm and smaller; electrodes for plasma arc cutting

US Imports: 30 mt (2019 est.)

Import Sources (2015–18): Hafnium, unwrought: Germany, 45%; France, 29%; China, 15%; United Kingdom, 11%; and other, <1%.

World Resources: World resources of hafnium are associated with those of zircon and baddeleyite. Quantitative estimates of hafnium resources are not available.

Substitutes: Silver-cadmium-indium control rods are used in lieu of hafnium at numerous nuclear power plants. Zirconium can be used interchangeably with hafnium in certain superalloys.

Note(s): Production of hafnium metal from hafnium oxide (HfO2) at the Dubbo Zirconia Project, in New South Wales, Australia, would be independent of zirconium metal refinement for the nuclear industry where it is a byproduct. Additional heavy-mineral exploration and mining projects are underway in Australia, Mozambique, Sri Lanka, and Tanzania.

Indium (In/49)

Description: Indium is a soft, malleable, silvery-white metallic element; it is produced mainly from residues generated during zinc ore processing.

Uses: LCD displays; organic LEDs; fiber-optics; solder and alloys; infrared imaging; communications

US Imports: 110 mt (2019 est.). The US is 100% import reliant for its indium needs.

Import Sources (2015–18): China, 36%; Canada, 22%; Republic of Korea, 11%; Taiwan, 7%; and other, 24%.

World Resources: Indium is most commonly recovered from the zinc-sulfide ore mineral sphalerite. The indium content of zinc deposits from which it is recovered ranges from less than 1 part per million to 100 parts per million.

Substitutes: Antimony tin oxide coatings have been developed as an alternative to indium tin oxide (ITO) coatings in LCDs and have been successfully annealed to LCD glass; carbon nanotube coatings have been developed as an alternative to ITO coatings in flexible displays, solar cells, and touch screens; PEDOT [poly(3,4-ethylene dioxythiophene)] has also been developed as a substitute for ITO in flexible displays and organic light-emitting diodes; and silver nanowires have been explored as a substitute for ITO in touch screens. Graphene has been developed to replace ITO electrodes in solar cells and also has been explored as a replacement for ITO in flexible touch screens. Researchers have developed a more adhesive zinc oxide nanopowder to replace ITO in LCDs. Gallium arsenide can substitute for indium phosphide in solar cells and in many semiconductor applications. Hafnium can replace indium in nuclear reactor control rod alloys.

Note(s): Indium was not recovered from ores in the US in 2019. Several companies produced indium products - including alloys, compounds, high-purity metal, and solders - from imported indium metal. Production of ITO continued to account for most of global indium consumption.

Lead (Pb/82)

Description: Lead is a very corrosion-resistant, dense, ductile, and malleable blue-gray metal that has been used for at least 5,000 years. The most significant lead mineral is galena (lead sulfide).

Uses: batteries; cable sheeting; solder; shielding (X-ray machines); ammunition

US Imports: 520,000 mt (2019 est.)

Import Sources (2013–16): Refined metal: Canada, 44%; Mexico, 18%; Republic of Korea, 17%; India, 5%; and other, 16%.

World Resources: Identified world lead resources total more than 2 billion tons. In recent years, significant lead resources have been identified in association with zinc and (or) silver or copper deposits in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, and the US (Alaska).

Substitutes: Substitution by plastics has reduced the use of lead in cable covering and cans. Tin has replaced lead in solder for potable water systems. The electronics industry has moved toward lead-free solders and flat-panel displays that do not require lead shielding. Steel and zinc are common substitutes for lead in wheel weights.

Note(s): According to the International Lead and Zinc Study Group, global refined lead production in 2019 decreased by 0.3% to 11.76 million tons, and metal consumption decreased by 0.5% to 11.81 million tons, resulting in a production-to-consumption deficit of about 50,000 tons of refined lead owing to the decline in automobile production and increased uses of lithium-ion batteries.

Lithium (Li/3)

Description: Lithium is a metallic element widely distributed in the earth's crust at low concentrations. Spodumene, petalite, and lepidolite are important mineral sources of lithium. Subsurface brines are the dominant raw material for lithium carbonate production worldwide because of lower production costs as compared with the costs for hard rock ores.

Uses: enamels; glass; ceramics; air purification; lithium ion-batteries; focal lenses for telescopes

US Imports: 2,500 mt (2019 est.)

Import Sources (2015–18): Argentina, 53%; Chile, 40%; China, 3%; and other, 4%.

World Resources: Owing to continuing exploration, identified lithium resources have increased substantially worldwide and total about 80 million tons. Lithium resources in the United States—from continental brines, geothermal brines, hectorite, oilfield brines, and pegmatites—are 6.8 million tons. Lithium resources in other countries have been revised to 73 million tons. Lithium resources, in descending order, are: Bolivia, 21 million tons; Argentina, 17 million tons; Chile, 9 million tons; Australia, 6.3 million tons; China, 4.5 million tons; Congo (Kinshasa), 3 million tons; Germany, 2.5 million tons; Canada and Mexico, 1.7 million tons each; Czechia, 1.3 million tons; Mali, Russia, and Serbia, 1 million tons each; Zimbabwe, 540,000 tons; Brazil, 400,000 tons; Spain, 300,000 tons; Portugal, 250,000 tons; Peru, 130,000 tons; Austria, Finland and Kazakhstan, 50,000 tons each; and Namibia, 9,000 tons.

Substitutes: Substitution for lithium compounds is possible in batteries, ceramics, greases, and manufactured glass. Examples are calcium, magnesium, mercury, and zinc as anode material in primary batteries; calcium and aluminum soaps as substitutes for stearates in greases; and sodic and potassic fluxes in ceramics and glass manufacture.

Note(s): Lithium supply security has become a top priority for technology companies in the US and Asia. Strategic alliances and joint ventures among technology companies and exploration companies continue to be established to ensure a reliable, diversified supply of lithium for battery suppliers and vehicle manufacturers.

Magnesium (Mg/12)

Description: Magnesium is the eighth most abundant element in the Earth’s crust, representing about 2% of its total mass; it belongs to the alkaline earth metal series. The metal is silvery white and is prized for its lightness and strength in alloys. Magnesium can be extracted from the minerals dolomite and carnallite, but it is most often obtained from seawater or well and lake brines.

Uses: refractory material in furnace linings for steel, iron, metals, glass and cement production; used in agricultural, chemical, and construction industries

US Imports: 55,000 mt (2019 est.)

Import Sources (2015–18): Israel, 25%; Canada, 24%; Mexico, 10%; United Kingdom, 10%; and other, 31%.

World Resources: Resources from which magnesium may be recovered range from large to virtually unlimited and are globally widespread. Resources of dolomite, serpentine, and magnesium-bearing evaporite minerals are enormous. Magnesium-bearing brines are estimated to constitute a resource in the billions of tons, and magnesium could be recovered from seawater along world coastlines.

Substitutes: Aluminum and zinc may substitute for magnesium in castings and wrought products. The relatively light weight of magnesium is an advantage over aluminum and zinc in castings and wrought products in most applications; however, its high cost is a disadvantage relative to these substitutes. For iron and steel desulfurization, calcium carbide may be used instead of magnesium. Magnesium is preferred to calcium carbide for desulfurization of iron and steel because calcium carbide produces acetylene in the presence of water.

Note(s): Producers in China dominate magnesium production, but several projects are under development to increase primary magnesium metal capacity elsewhere.

Manganese (Mn/25)

Description: Manganese is a very brittle but hard metallic element. Pyrolusite (manganese dioxide (MnO2) is the main ore mineral for manganese. Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties.

Uses: steelmaking; aluminum alloy production; additive in unleaded gasoline; glass making and coloring; batteries and dry cells; alloys for chemical processing applications; alloys for high temperature bolts and fasteners

US Imports: Manganese ore 340,000 mt; Ferromanganese 370,000; Silicomanganese 370,000 mt (2019 est.). The US is 100% import reliant for its manganese needs.

Import Sources (2015–18): Manganese ore: Gabon, 70%; South Africa, 17%; Australia, 6%; Mexico, 5%; and other, 2%; Ferromanganese: South Africa, 27%; Australia, 19%; Norway, 16%; Republic of Korea, 13%; and other, 25%; Silicomanganese: Georgia, 27%; South Africa, 24%; Australia, 20%; Mexico, 8%; and other, 21%.

World Resources: Land-based manganese resources are large but irregularly distributed. South Africa accounts for about 74% of the world’s identified manganese resources, and Ukraine accounts for about 10%. Those in the US are very low grade and have potentially high extraction costs.

Substitutes: Manganese has no satisfactory substitute in its major applications.

Mercury (Hg/80)

Description: Mercury is the only common metal that is liquid at room temperature. It occurs either as native metal or in cinnabar, corderoite, livingstonite, and other minerals. Mercury has uniform volumetric thermal expansion, good electrical conductivity, and easily forms amalgams with almost all common metals except iron.

Uses: munition fuzes; missile and space guidance system gyroscopes; dental equipment; electric lighting; infrared detection

US Imports: 10 mt (2019 est.)

Import Sources (2015–18): Canada, 39%; France, 32%; Switzerland, 13%; China, 8%; and other, 8%.

World Resources: China, Kyrgyzstan, Mexico, Peru, Russia, Slovenia, Spain, and Ukraine have most of the world’s estimated 600,000 tons of mercury resources. Mexico reclaims mercury from Spanish colonial silver-mining waste. In Spain, once a leading producer of mercury, mining at its centuries-old Almaden Mine stopped in 2003. In the US, there are mercury occurrences in Alaska, Arkansas, California, Nevada, and Texas; however, mercury has not been mined as a principal mineral commodity since 1992. The declining consumption of mercury, except for small-scale gold mining, indicates that these resources are sufficient for centuries of use.

Substitutes: Ceramic composites substitute for the dark-gray mercury-containing dental amalgam. “Galistan,” an alloy of gallium, indium, and tin, replaces the mercury used in traditional mercury thermometers, and digital thermometers have replaced traditional thermometers. At chloralkali plants around the world, mercury-cell technology is being replaced by newer diaphragm and membrane cell technology. LEDs that contain indium substitute for mercury-containing fluorescent lamps. Lithium, nickel-cadmium, and zinc-air batteries replace mercury-zinc batteries in the US; indium compounds substitute for mercury in alkaline batteries; and organic compounds have been substituted for mercury fungicides in latex paint.

Note(s): Owing to mercury toxicity and concerns for the environment and human health, overall mercury use has declined in the US. Mercury continues to be released to the environment from numerous sources, including mercury-containing car switches when automobiles are scrapped without recovering them for recycling, coal-fired power plant emissions, and incineration of mercury-containing medical devices. Mercury is no longer used in batteries and paints manufactured in the US.

Molybdenum (Mo/42)

Description: Molybdenum is a refractory metallic element used principally as an alloying agent in steel, cast iron, and superalloys to enhance hardenability, strength, toughness, and wear and corrosion resistance. The mineral molybdenite (molybdenum sulfide) is an important source of molybdenum.

Uses: component in tool and alloy steels; component in nickel superalloys for high temperature sections of jet engines; lubricant; colorant; nickel superalloys for high temperature sections of turbine engines

US Imports: 37,000 mt (2019 est.)

Import Sources (2015–18): Molybdenum ores and concentrates: Peru, 53%; Chile, 27%; Canada, 11%; Mexico, 8%; and other, 1%.

World Resources: Global molybdenum production in 2019 decreased slightly compared with 2018. In descending order of production, China, Chile, the United States, Peru, and Mexico provided more than 90% of total global production. Identified resources of molybdenum in the US are about 5.4 million tons, and in the rest of the world, about 20 million tons. Molybdenum occurs as the principal metal sulfide in large low-grade porphyry molybdenum deposits and as an associated metal sulfide in low-grade porphyry copper deposits. Resources of molybdenum are adequate to supply world needs for the foreseeable future.

Substitutes: There is little substitution for molybdenum in its major application in steels and cast irons. Potential substitutes include boron, chromium, niobium (columbium), and vanadium in alloy steels; tungsten in tool steels; graphite, tantalum, and tungsten for refractory materials in high-temperature electric furnaces; and cadmium-red, chrome-orange, and organic-orange pigments for molybdenum orange.

Nickel (Ni/28)

Description: Nickel is a silvery metallic element. Most of the nickel mined comes from two types of deposits: laterites where the principal minerals are nickeliferous limonite (hydrated iron oxide) and garnierite (hydrous nickel silicate), or magmatic sulfide deposits where the principal mineral is pentlandite (iron nickel sulfide).

Uses: land based turbines; turbines for jet aircraft engines; turbines for large-scale power generation; liquid gas storage; high speed steels

US Imports: 120,000 mt (2019 est.)

Import Sources (2015–18): Canada, 41%; Norway, 11%; Australia, 8%; Finland, 8%; and other, 32%.

World Resources: Identified land-based resources averaging 1% nickel or greater contain at least 130 million tons of nickel, with about 60% in laterites and 40% in sulfide deposits. Extensive nickel resources also are found in manganese crusts and nodules on the ocean floor. The decline in discovery of new sulfide deposits in traditional mining districts has led to exploration in more challenging locations such as east-central Africa and the subarctic.

Substitutes: Low-nickel, duplex, or ultrahigh-chromium stainless steels are being substituted for austenitic grades in construction. Nickel-free specialty steels are sometimes used in place of stainless steel in the power-generating and petrochemical industries. Titanium alloys can substitute for nickel metal or nickel-base alloys in corrosive chemical environments. Lithium-ion batteries may be used instead of nickel metal hydride batteries in certain applications.

Note(s): In the US, the leading uses for primary nickel are stainless and alloy steels, nonferrous alloys and superalloys, electroplating, and other uses including catalysts and chemicals. Domestic production of stainless steel was estimated to have decreased by approximately 10% in 2019. Consumption of nickel used in alloys for jet turbine engines continued to increase.

 

Niobium (Nb/41)

Description: Columbium and niobium are synonymous names for the chemical element with atomic number 41; columbium was the name given in 1801, and niobium (Nb) was the name officially designated by the International Union of Pure and Applied Chemistry in 1950. The US does not have a niobium mining industry because identified resources are low grade. Brazil and Canada are the major producers of niobium mineral concentrates.

Uses: alloying element in steels, stainless steels, superalloys (nickel, cobalt, and iron-based); jet engine components; gas turbines; heat resistant and combustion equipment; tool bits and cutting tools

US Imports: 11,000 mt (2019 est.). The US is 100% import reliant for its niobium needs.

US Import Sources (2015–18): Niobium ore and concentrate: Rwanda, 39%; Brazil, 19%; Australia, 16%; Congo (Kinshasa), 10%; and other, 16%. Niobium oxide: Brazil, 48%; Russia, 25%; Thailand, 10%; Estonia, 9%; and other, 8%. Ferroniobium and niobium metal: Brazil, 70%; Canada, 26%; Germany, 2%; and other, 2%. Total imports: Brazil, 67%; Canada, 23%; Russia, 3%; Germany, 2%; and other, 5%. Of the US niobium material imports, 75% was ferroniobium, 14% was niobium metal, 10% was niobium oxide, and 1% was niobium ores and concentrates.

World Resources: Brazil continues to be the world’s leading niobium producer with 88% of global production, followed by Canada with 10%. World resources of niobium are more than adequate to supply projected needs. Most of the world’s identified resources of niobium fall outside the US. The United States has approximately 1,400,000 tons of niobium in identified resources, most of which were considered uneconomical at 2019 prices for niobium.

Substitutes: The following materials can be substituted for niobium, but a performance loss or higher cost may ensue: molybdenum and vanadium, as alloying elements in high-strength low-alloy steels; tantalum and titanium, as alloying elements in stainless- and high-strength steels; and ceramics, molybdenum, tantalum, and tungsten in high temperature applications.

Note(s): Significant US niobium mine production has not been reported since 1959. Niobium principally is imported in the form of ferroniobium.

Rhenium (Re/75)

Description: Rhenium is a silvery-gray, heavy, transition metal. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the earth's crust. Rhenium has the third-highest melting point and second-highest boiling point of any element. Rhenium resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores.

Uses: superalloys used in high-temperature turbine engine components; petroleum-reforming catalysts

US Imports: 39 mt (2019 est.)

Import Sources (2015–18): Ammonium perrhenate: Kazakhstan, 29%; Canada, 20%; Germany, 14%; China, 8%; and other, 29%. Rhenium metal powder: Chile, 83%; Germany, 7%; Belgium, 3%; Poland, 3%; and other, 4%. Total: Chile, 62%; Germany, 8%; Kazakhstan, 8%; Canada, 7%; and other, 15%.

World Resources: Most rhenium occurs with molybdenum in porphyry copper deposits. Identified US resources are estimated to be about 5 million kilograms, and the identified resources of the rest of the world are approximately 6 million kilograms. Rhenium also is associated with copper minerals in sedimentary deposits in Armenia, Kazakhstan, Poland, Russia, and Uzbekistan, where ore is processed for copper recovery and the rhenium-bearing residues are recovered at copper smelters.

Substitutes: Substitutes for rhenium in platinum-rhenium catalysts are being evaluated continually. Iridium and tin have achieved commercial success in one such application. Other metals being evaluated for catalytic use include gallium, germanium, indium, selenium, silicon, tungsten, and vanadium. The use of these and other metals in bimetallic catalysts might decrease rhenium’s share of the existing catalyst market; however, this would likely be offset by rhenium-bearing catalysts being considered for use in several proposed gas-to-liquid projects. Materials that can substitute for rhenium in various end uses are as follows: cobalt and tungsten for coatings on copper x-ray targets, rhodium and rhodium-iridium for high-temperature thermocouples, tungsten and platinum-ruthenium for coatings on electrical contacts, and tungsten and tantalum for electron emitters.

Note(s): During 2019, the US continued to rely on imports for much of its supply of rhenium, which came primarily from Canada, Chile, Germany, and Kazakhstan.

Rubidium (Rb/37)

Description: Rubidium is a soft, ductile, silvery-white metal that melts at 39.3 °C. Naturally occurring rubidium is slightly radioactive. Rubidium is an extremely reactive metal - it ignites spontaneously in the presence of air and decomposes water explosively, igniting the liberated hydrogen.

Uses: Rubidium is used interchangeably or together with cesium in many uses; its principal application is in specialty glasses used in fiber optic telecommunication systems; Rubidium’s photoemissive properties have led to its use in night-vision devices, photoelectric cells, and photomultiplier tubes; it has several uses in medical science, such as in positron emission tomographic (PET) imaging, the treatment of epilepsy, and the ultracentrifugal separation of nucleic acids and viruses.

US imports: US salient statistics, such as consumption, exports, and imports, are not available. Some concentrate was imported to the US for further processing. Industry information during the past decade suggests a domestic consumption rate of approximately 2,000 kilograms per year. The US was 100% import reliant for rubidium minerals.

Import sources: No reliable data has been available to determine the source of rubidium ore imported by the United States since 1988. Previously, Canada was thought to be the primary supplier of rubidium ore.

World Resources: Although rubidium is more abundant in the earth’s crust than copper, lead, or zinc, it forms no minerals of its own, and is, or has been, produced in small quantities as a byproduct of the processing of cesium and lithium ores taken from a few small deposits in Canada, Namibia, and Zambia.

Substitutes: Cesium and rubidium can be used interchangeably in many applications because they have similar physical properties and atomic radii.

Strontium (Sr/38)

Description: Strontium is a silvery-white metal, found in nature in two minerals, celestite (strontium sulfate) and strontianite (strontium carbonate).

Uses: alloys; pyrotechnics; ceramics and glasses; electrolytic production of zinc; tracer ammunition

US Imports: celestite – 11,000 mt; strontium compounds – 6,300 mt (2019 est.). The US is 100% import reliant for its strontium needs.

Import Sources (2015–18): Celestite: Mexico, 100%. Strontium compounds: Mexico, 53%; Germany, 37%; China, 7%; and other, 3%. Total imports: Mexico, 87%; Germany, 10%; China, 2%; and other, 1%.

World Resources: World resources of strontium are thought to exceed 1 billion tons. All of the celestite is imported from Mexico and is thought to be used exclusively as an additive in drilling fluids for oil and natural gas exploration and production. For these applications, celestite is ground but undergoes no chemical processing. Outside the US, celestite is the raw material used for production of strontium compounds.

Substitutes: Barium can be substituted for strontium in ferrite ceramic magnets; however, the resulting barium composite will have reduced maximum operating temperature when compared with that of strontium composites. Substituting for strontium in pyrotechnics is hindered by difficulty in obtaining the desired brilliance and visibility imparted by strontium and its compounds.

Note(s): Strontium carbonate is sintered with iron oxide to produce permanent ceramic ferrite magnets. Strontium nitrate contributes a brilliant red color to fireworks and signal flares.

Tantalum (Ta/73)

Description: Tantalum is a metallic element that is ductile, easily fabricated, highly resistant to corrosion by acids, and a good conductor of heat and electricity with a high melting point. The major use for tantalum, as tantalum metal powder, is in the production of electronic components, mainly tantalum capacitors. Major end uses for tantalum capacitors include portable telephones, pagers, personal computers, and automotive electronics. Alloyed with other metals, tantalum is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components.

Uses: chemical processing equipment; heat exchangers; anti-lock brake systems; high temperature aerospace engine parts; night vision goggles; global positioning systems; missile systems

US Imports: 1,300 mt (2019 est.). The US is 100% import reliant for its tantalum needs.

Import Sources (2015–18): Tantalum minerals: Rwanda, 39%; Brazil, 20%; Australia, 17%; Congo (Kinshasa), 10%; and other, 14%. Tantalum metal: China, 39%; Germany, 19%; Kazakhstan, 14%; Thailand, 12%; and other, 16%. Tantalum waste and scrap: Mexico, 14%; Austria, 11%; Japan, 10%; Germany, 9%; and other, 56%.

World Resources: Identified resources of tantalum, most of which are in Australia, Brazil, and Canada, are considered adequate to meet projected needs. The US has about 55,000 tons of tantalum resources in identified deposits, most of which are considered uneconomic at 2019 prices.

Substitutes: The following materials can be substituted for tantalum, but usually with less effectiveness: niobium in carbides; aluminum and ceramics in electronic capacitors; glass, niobium, platinum, titanium, and zirconium in corrosion-resistant applications; and hafnium, iridium, molybdenum, niobium, rhenium, and tungsten in high-temperature applications.

Note(s): No significant US tantalum mine production has been reported since 1959. Domestic tantalum resources are of low grade, some are mineralogically complex, and most are not commercially recoverable. Companies in the US produce tantalum alloys, capacitors, compounds, and metal from imported tantalum ores and concentrates, tantalum-containing materials, and metal and alloys recovered from foreign and domestic scrap.

Tin (Sn/50)

Description: Tin is a silvery-white metallic element. The most important ore mineral of tin, cassiterite (tin dioxide), is formed in high-temperature veins that are usually related to igneous rocks such as granites and rhyolites. It is often found in association with tungsten minerals.

Uses: bearings; containers; solder; bronze; chemicals; LCD TVs, touch screens and portable electronics

US Imports: refined – 35,000 mt (2019 est.)

Import Sources (2015–18): Indonesia, 25%; Malaysia, 24%; Peru, 20%; Bolivia, 18%; and other, 13%.

World Resources: World resources, principally in western Africa, southeastern Asia, Australia, Bolivia, Brazil, Indonesia, and Russia, are extensive and, if developed, could sustain recent annual production rates well into the future.

Substitutes: Aluminum, glass, paper, plastic, or tin-free steel substitute for tin content in cans and containers. Other materials that substitute for tin are epoxy resins for solder; aluminum alloys, alternative copper-base alloys, and plastics for bronze; plastics for bearing metals that contain tin; and compounds of lead and sodium for some tin chemicals.

Note(s): Identified resources of tin in the US, primarily in Alaska, are insignificant compared with those of the rest of the world. Tin has not been mined or smelted in the US since 1993 and 1989, respectively.

Titanium (Ti/22)

Description: Titanium is a hard, silvery-white metallic element. As a metal, titanium is well known for corrosion resistance and for its high strength-to-weight ratio. When titanium metal is produced from ore, it is first produced in sponge form before it is melted into metal shapes. Titanium dioxide pigment is a white pigment characterized by its purity, refractive index, particle size, and surface properties. Titanium metal and pigment are produced from the minerals ilmenite, leucoxene, and rutile.

Uses: landing gear, springs, rotors (helicopter), fittings, and attachments; structural components for airplanes, satellites, and spacecraft; gas turbine engines; chemical processing

US Imports: 27,000 mt (2019 est.)

Import Sources (2015–18): Sponge metal: Japan, 86%; Kazakhstan, 8%; Ukraine, 4%; China, 1%; and Russia, 1%. Titanium dioxide pigment: Canada, 35%; China, 25%; Germany, 9%; Mexico, 4%; and other, 27%.

World Resources: Ilmenite accounts for about 89% of the world’s consumption of titanium minerals. World resources of anatase, ilmenite, and rutile total more than 2 billion tons.

Substitutes: Few materials possess titanium metal’s strength-to-weight ratio and corrosion resistance. In high-strength applications, titanium competes with aluminum, composites, intermetallics, steel, and superalloys. Aluminum, nickel, specialty steels, and zirconium alloys may be substituted for titanium for applications that require corrosion resistance. Ground calcium carbonate, precipitated calcium carbonate, kaolin, and talc compete with titanium dioxide as a white pigment.

Note(s): In 2019, an estimated 80% of titanium metal was used in aerospace applications; the remaining 20% was used in armor, chemical processing, marine hardware, medical implants, power generation, and consumer and other applications.

Tungsten (W/74)

Description: Tungsten is a gray-white metallic element; it has the highest melting temperature of all elements except carbon and is one of the heaviest elements. Tungsten is produced from the mineral ores scheelite (calcium tungstate) and wolframite (iron-manganese tungstate). The ore is concentrated and then usually produced into the intermediate product ammonium paratungstate (APT) before being processed into metallic applications. The US does not have any operating tungsten mines.

Uses: steels; wear-resistant alloys; component in nickel superalloys for high-temperature sections of jet engines; armor penetrating projectiles; aircraft weights and counterweights; small arms ammunition

US Imports: 13,800 mt (2019 est.)

Import Sources (2015–18): Tungsten contained in ores and concentrates, intermediate and primary products, wrought and unwrought tungsten, and waste and scrap: China, 31%; Bolivia, 10%; Germany, 9%; Spain, 6%; and other, 44%.

World Resources: World tungsten resources are geographically widespread. China ranks first in the world in terms of tungsten resources and reserves and has some of the largest deposits. Canada, Kazakhstan, Russia, and the US also have significant tungsten resources.

Substitutes: Potential substitutes for cemented tungsten carbides include cemented carbides based on molybdenum carbide and titanium carbide, ceramics, ceramic-metallic composites (cermets), and tool steels. Potential substitutes for other applications are as follows: molybdenum for certain tungsten mill products; molybdenum steels for tungsten steels; lighting based on carbon nanotube filaments, induction technology, and light-emitting diodes for lighting based on tungsten electrodes or filaments; depleted uranium or lead for tungsten or tungsten alloys in applications requiring high-density or the ability to shield radiation; and depleted uranium alloys or hardened steel for cemented tungsten carbides or tungsten alloys in armor-piercing projectiles.

Note(s): World tungsten supply was dominated by production in China and exports from China. China was the world’s leading tungsten consumer. There has been no known domestic commercial production of tungsten concentrates since 2015.

Uranium (U/92)

Description: Uranium is a common metal found in rocks all over the world. Uranium occurs in combination with small amounts of other elements.

Uses: Uranium is the fuel most widely used by nuclear power plants for nuclear fission. In nuclear fission, energy is released when atoms are split apart to form smaller atoms. Nuclear power plants use the heat from nuclear fission to produce electricity.

US Imports: 18,824 mt (2018)

Import Sources (2018): Canada, 24%; Australia, 18%; Russia, 13%; Kazakhstan, 20%; Uzbekistan, 6%; Hungary, Malawi, Namibia, Niger, South Africa, Ukraine, and unknown, 3%

World Resources: Economically recoverable uranium deposits have been discovered primarily in the western US, Australia, Canada, Central Asia, Africa, and South America. About 10% of the uranium delivered to US reactors in 2018 was produced in the US and 90% came from other countries.

Substitutes: None

Note(s): Nuclear power plants use a certain type of uranium, U-235, as fuel because its atoms are easily split apart. Although uranium is about 100 times more common than silver, U-235 is relatively rare. After uranium is mined, the U-235 must be extracted and processed before it can be used as a fuel. Mined uranium ore typically yields 0.5 to 2 kg (1 to 4 pounds) of uranium concentrate (U3O8 or yellowcake) per ton, or 0.05% to 0.20% yellowcake.

Vanadium (V/23)

Description: Vanadium is a soft, silver-gray metallic element. There is no single mineral ore from which vanadium is recovered. However, it is found as a trace element in a several types of rock and is a by-product of other mining operations. Vanadinite (lead chlorovanadate) is mineral that contains vanadium.

Uses: steel; Titanium-Aluminum-Vanadium alloys in jet engines and high-speed aircraft; cladding titanium to steel; energy storage

US Imports: Ferrovanadium 2,500 mt; Vanadium pentoxide 4,000 mt (2019 est.) The US is 100% import reliant for its vanadium needs.

Import Sources (2015–18): Ferrovanadium: Austria, 48%; Canada, 22%; Russia, 14%; Republic of Korea, 11%; and other, 5%. Vanadium pentoxide: South Africa, 44%; Brazil, 29%; China, 11%; Taiwan, 6%; and other, 10%.

World Resources: World resources of vanadium exceed 63 million tons. Vanadium occurs in deposits of phosphate rock, titaniferous magnetite, and uraniferous sandstone and siltstone, in which it constitutes less than 2% of the host rock. Significant quantities are also present in bauxite and carboniferous materials, such as coal, crude oil, oil shale, and tar sands. Because vanadium is typically recovered as a byproduct or coproduct, demonstrated world resources of the element are not fully indicative of available supplies.

Substitutes: Steels containing various combinations of other alloying elements can be substituted for steels containing vanadium. Certain metals, such as manganese, molybdenum, niobium (columbium), titanium, and tungsten, are to some degree interchangeable with vanadium as alloying elements in steel. Platinum and nickel can replace vanadium compounds as catalysts in some chemical processes. Currently, no acceptable substitute for vanadium is available for use in aerospace titanium alloys.

Note(s): Although US resources and secondary recovery are adequate to supply a large portion of domestic needs, all of US demand is currently met by foreign sources. Metallurgical use, primarily as an alloying agent for iron and steel, accounted for about 94% of US domestic vanadium consumption in 2019.

Zinc (Zn/30)

Description: Zinc is a blue-gray, metallic element; it is recovered from a number of different zinc minerals, the most significant of which is sphalerite (zinc sulfide). Other minerals, such as smithsonite (zinc carbonate) and zincite (zinc oxide), are also zinc ores.

Uses: galvanized steel; bronze and brass; solder; batteries; solar cells

US Imports: Ore and refined metal – 830,000 mt (2019 est.)

Import Sources (2015–18): Ore and concentrate: Peru, 98%; and other, 2%. Refined metal: Canada, 64%; Mexico, 13%; Australia, 7%; Peru, 7%; and other, 9%.

World Resources: Identified zinc resources of the world are about 1.9 billion tons. Global zinc mine production in 2019 was estimated to be 13 million tons, a 4% increase from that of 2018. Notable zinc mine production increases took place in Australia, China, and South Africa.

Substitutes: Aluminum and plastics substitute for galvanized sheet in automobiles; aluminum alloys, cadmium, paint, and plastic coatings replace zinc coatings in other applications. Aluminum- and magnesium-base alloys are major competitors for zinc-base die-casting alloys. Many elements are substitutes for zinc in chemical, electronic, and pigment uses.

Zirconium (Zr/40)

Description: Zircon is a zirconium silicate mineral that is usually 98% zirconium and 2% hafnium and is the primary source of both materials. Zirconium is a metallic element used in a number of industrial applications because it is so resistant to corrosion and high temperatures.

Uses: space vehicles and parts; abrasives; alloys for naval applications; metallurgical furnaces; ceramic knives; artificial joints and limbs

US Imports: 26,520 mt (2019 est.)

Import Sources (2015–18): Zirconium ores and concentrates: South Africa, 53%; Senegal, 28%; Australia, 15%; Russia, 2%; and other, 2%.

World Resources: Resources of zircon in the US included about 14 million tons associated with titanium resources in heavy-mineral-sand deposits. Phosphate rock and sand and gravel deposits could potentially yield substantial amounts of zircon as a byproduct.

Substitutes: Chromite and olivine can be used instead of zircon for some foundry applications. Dolomite and spinel refractories can also substitute for zircon in certain high-temperature applications.

Note(s): The leading consumers of zirconium metal are the chemical process and nuclear energy industries.

Metals, precious

Iridium (Ir/77)

Description: Iridium, the second densest element, is silvery-white that resembles platinum but with a slightly yellow tint. It is hard and brittle with a high boiling point that makes it difficult to use or work. Iridium is the most corrosion-resistant metal; it has handling temperatures as high as 2,000ºC, but in a powder or dust form it is highly reactive and flammable.

Uses: spark plug tips; backlit LED screens and organic LEDS; platinum hardening agent; iridium alloys used in aircraft engines; guided missile systems; computers and radar screens; military semiconductors

US Imports: .91 mt (2019 est.)

Palladium (Pd/46)

Description: Palladium, like other platinum group metals (PGMs), is a rare, silvery-white metal found in the earth’s crust. When annealed, it is a soft, ductile, noble  metal that does not tarnish in air below 800ºC. The strength and hardness of palladium can be increased by cold-working. It has the lowest boiling point (2,963ºC) and is the least dense of all PGMs. Palladium has a unique ability to absorb hydrogen at up to 900 times its own volume.

Uses: electronic conductive connectors; automotive catalysts; multilayer ceramic capacitors; internal computer components; aerospace brazing and soldering

US Imports: 76 mt (2019 est.)

Import Sources (2015–18): South Africa, 33%; Russia, 33%; Germany, 7%; Italy, 7%; and other, 20%.

World Resources: World resources of PGMs are estimated to total more than 100 million kilograms. The largest reserves are in the Bushveld Complex in South Africa.

Substitutes: For some industrial end uses, one PGM can substitute for another, but with losses in efficiency.

Note(s): Palladium is used for investments as an exchange-traded product and in individual holdings of physical bars and coins.

Platinum (Pt/78)

Description: Platinum, one of the rarest elements found in the Earth’s crust, has a silvery-white color that never tarnishes. It is a dense, ductile metal that is malleable. Platinum, a noble metal, is corrosion-resistant with high-temperature stability and is non-oxidizable with stable electrical properties. It is part of a group of metals known as the platinum group metals (PGMs).

Uses: LCD/flat panel displays; catalysts (automotive, bulk chemical, petroleum refining); high-temperature, corrosion-resistant alloy; aircraft turbine blades; coatings; engine seals and gaskets

US Imports: 38 mt (2019 est.)

Import Sources (2015–18): South Africa, 46%; Germany, 16%; Italy, 7%; Russia, 6%; and other, 25%.

World Resources: World resources of PGMs are estimated to total more than 100 million kilograms. The largest reserves are in the Bushveld Complex in South Africa.

Substitutes: Palladium has been substituted for platinum in most gasoline-engine catalytic converters because of the historically lower price for palladium relative to that of platinum. About 25% of palladium can routinely be substituted for platinum in diesel catalytic converters; the proportion can be as much as 50% in some applications.

Note(s): Platinum is used for investments as an exchange-traded product and in individual holdings of physical bars and coins.

Silver (Ag/47)

Description: A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. The physical properties of silver include high ductility, electrical conductivity, malleability, and reflectivity.

Uses: antimicrobial bandages; clothing; pharmaceuticals; plastics; batteries; bearings; brazing and soldering; catalytic converters in automobiles; electroplating; inks; mirrors; photovoltaic solar cells; water purification; wood treatment

US Imports: 4,700 mt (2019 est.)

Import Sources (2015–18): Mexico, 48%; Canada, 29%; Peru, 5%; Poland, 4%; and other, 14%.

World Resources: Although silver was a principal product at several mines, silver was primarily obtained as a byproduct from lead-zinc mines, copper mines, and gold mines, in descending order of production. The polymetallic ore deposits from which silver was recovered account for more than two-thirds of US and world resources of silver. Most recent silver discoveries have been associated with gold occurrences; however, copper and lead-zinc occurrences that contain byproduct silver will continue to account for a significant share of reserves and resources in the future. World silver mine production decreased in 2017 to 25,000 tons, principally as a result of decreased production from mines in Argentina, Australia, Bolivia, Chile, Peru, and the US.

Substitutes: Digital imaging, film with reduced silver content, silverless black-and-white film, and xerography substitute for traditional photographic applications for silver. Surgical pins and plates may be made with stainless steel, tantalum, and titanium in place of silver. Stainless steel may be substituted for silver flatware. Non-silver batteries may replace silver batteries in some applications. Aluminum and rhodium may be used to replace silver that was traditionally used in mirrors and other reflecting surfaces. Silver may be used to replace more costly metals in catalytic converters for off-road vehicles.

Note(s): In 2019, the estimated domestic uses for silver were electrical and electronics, 30%; jewelry and silverware, 26%; coins and medals, 12%; photography, 3%; and other, 29%.

 

Non-metals

Arsenic (As/33)

Description: Arsenic is a gray, yellow, or black metalloid that is generally recovered as a by-product from other metal processing. The brittle gray form used by industry is the most common form.

Uses: high-purity arsenic (99.9999%) is used to produce Gallium-Arsenide (GaAs) semiconductors for solar cells, space research, and telecommunications; used for Germanium-Arsenide-Selenide specialty optical materials; Indium-Gallium-Arsenide (InGaAs) is used for short-wave infrared technology; lead-hardening alloy for use in ammunition and batteries; pesticides, herbicides, Chromated-Copper-Arsenide (CCA) wood preservative

US imports: Arsenic metal 400 mt, Arsenic compounds 7,000 mt (2019 est.). The US is 100% import reliant for its arsenic needs.

Import Sources (2015–18): Arsenic metal: China, 93%; Japan, 4%; Hong Kong, 3%, and other, <1%. Arsenic trioxide: China, 50%; Morocco, 47%; Belgium, 2%; and other, 1%.

World Resources: Arsenic may be obtained from copper, gold, and lead smelter flue dust, as well as from roasting arsenopyrite, the most abundant ore mineral of arsenic. Arsenic has been recovered from orpiment and realgar in China, Peru, and the Philippines, as well as from copper-gold ores in Chile; it was associated with gold occurrences in Canada. Orpiment and realgar from gold mines in Sichuan Province, China, were stockpiled for later recovery of arsenic. Arsenic also may be recovered from enargite, a copper mineral. Arsenic trioxide was produced at the hydrometallurgical complex of Guemassa, near Marrakech, Morocco, from cobalt arsenide ore from the Bou-Azzer Mine.

Substitutes: Substitutes for CCA in wood treatment include alkaline copper quaternary, ammoniacal copper quaternary, ammoniacal copper zinc arsenate, alkaline copper quaternary boron-based preservatives, copper azole, copper citrate, and copper naphthenate. Treated wood substitutes include concrete, plastic composite material, plasticized wood scrap, or steel. Silicon-based complementary metal-oxide semiconductor power amplifiers compete with GaAs power amplifiers in mid-tier 3G cellular handsets. Indium phosphide components can be substituted for GaAs-based infrared laser diodes in some specific-wavelength applications, and helium-neon lasers compete with GaAs in visible laser diode applications. Silicon is the principal competitor with GaAs in solar-cell applications. GaAs-based integrated circuits are used in many defense-related applications because of their unique properties, and no effective substitutes exist for GaAs in these applications. GaAs in heterojunction bipolar transistors is being replaced in some applications by silicon-germanium.

Note(s): China and Morocco continued to be the leading global producers of arsenic trioxide, accounting for about 90% of estimated world production and supplied almost all of US imports of arsenic trioxide in 2019. China was the leading world producer of arsenic metal and supplied about 90% of US arsenic metal imports in 2019.

Boron (B/5)

Description: Boron is a relatively rare element representing only 0.001% of the earth’s crust. It is a metalloid with properties that are in-between or a mixture of those of metals and nonmetals. Ordinary elemental boron is a brown-black, amorphous powder. Pure boron can be made into extremely hard yellow monoclinic crystals with semiconductor properties much like silicon. Boron has two naturally occurring and stable isotopes, 11B (80.1%) and 10B (19.9%). Although the term “boron” is commonly referenced, it does not occur in nature in an elemental state. Boron combines with oxygen and other elements to form boric acid, or inorganic salts called borates. Boric acid is sometimes found in volcanic spring waters. Boron compounds, chiefly borates, are commercially important. Four borates - colemanite, kernite, tincal, and ulexite - make up 90% of the borates used by industry worldwide.

Uses: component of composite materials (boron fibers) in advanced aerospace structures; industrial catalyst for many organic reactions, such as polymerization reactions; major role in electroplating of nickel, lead and tin; inner plates of ballistic vests and for tank armor (carbon boride); permanent Neodymium-Iron-Boron (NdFeB) magnets

US Imports: Refined borax – 150,000 mt, Boric acid – 50,000 mt, Borates – 75,000 mt (2019 est.)

Import Sources (2015–18): All forms: Turkey, 80%; Bolivia, 13%; Chile, 3%; and other, 4%.

World Resources: Deposits of borates are associated with volcanic activity and arid climates, with the largest economically viable deposits located in the Mojave Desert of the US, the Alpide belt in southern Asia, and the Andean belt of South America. US deposits consist primarily of tincal, kernite, and borates contained in brines, and to a lesser extent ulexite and colemanite. About 70% of all deposits in Turkey are colemanite, primarily used in the production of heat-resistant glass. At current levels of consumption, world resources are adequate for the foreseeable future.

Substitutes: The substitution of other materials for boron is possible in detergents, enamels, insulation, and soaps. Sodium percarbonate can replace borates in detergents and requires lower temperatures to undergo hydrolysis, which is an environmental consideration. Some enamels can use other glass-producing substances, such as phosphates. Insulation substitutes include cellulose, foams, and mineral wools. In soaps, sodium and potassium salts of fatty acids can act as cleaning and emulsifying agents.

Germanium (Ge/32)

Description: Germanium is mainly a byproduct of zinc ore processing. It is a hard, grayish-white element and has a metallic luster and the same crystal structure as diamond; it is also brittle, like glass. Germanium is a semiconductor, with electrical properties between those of a metal and an insulator.

Uses: polymerization catalyst for polyethylene terephthalates (PET); telecommunication fiber optics; lenses for mid- and long- wavelength infrared (IR) devices; solar cells

US Imports: 14 mt (2019 est.)

Import Sources (2015–18): Germanium metal: China, 59%; Belgium, 22%; Germany, 9%; Russia, 7%; and other, 3%.

World Resources: In 2019, China remained the leading global producer of germanium. The available resources of germanium are associated with certain zinc and lead-zinc-copper sulfide ores. Substantial US reserves of recoverable germanium are contained in zinc deposits in Alaska and Tennessee. Based on an analysis of zinc concentrates, US reserves of zinc may contain as much as 2,500 tons of germanium. Because zinc concentrates are shipped globally and blended at smelters, however, the recoverable germanium in zinc reserves cannot be determined. On a global scale, as little as 3% of the germanium contained in zinc concentrates is recovered. Significant amounts of germanium are contained in ash and flue dust generated in the combustion of certain coals for power generation.

Substitutes: Silicon can be a less-expensive substitute for germanium in certain electronic applications. Some metallic compounds can be substituted in high-frequency electronics applications and in some light-emitting-diode applications. Zinc selenide and germanium glass substitute for germanium metal in infrared applications systems, but often at the expense of performance. Antimony and titanium are substitutes for use as polymerization catalysts.

Note(s): Germanium-containing infrared optics are primarily for military use, but the demand for thermal-imaging devices that use germanium lenses increased during the past few years. Fiber-optic cable manufacturing accounted for about one-third of global germanium consumption.

Graphite / Carbon (C/6)

Description: 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. 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.

Uses: The major uses of natural graphite in 2018 were brake linings, lubricants, powdered metals, refractory applications, and steelmaking. 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.

US Imports: 58,000 mt (2019 est.). The US is 100% import reliant for its graphite needs.

Import Sources (2015–18): China, 33%; Mexico, 24%; Canada, 16%; India, 9%; and other, 18%.

World Resources: US domestic resources of graphite are relatively small, but the rest of the world’s inferred resources exceed 800 million tons of recoverable graphite.

Substitutes: Synthetic graphite powder, scrap from discarded machined shapes, and calcined petroleum coke compete for use in iron and steel production. Synthetic graphite powder and secondary synthetic graphite from machining graphite shapes compete for use in battery applications. Finely ground coke with olivine is a potential competitor in foundry-facing applications. Molybdenum disulfide competes as a dry lubricant but is more sensitive to oxidizing conditions.

Note(s):During 2019, China produced more than 60% of the world’s graphite. Approximately 40% of production in China was amorphous graphite and about 60% was flake. Large graphite deposits were being developed in Madagascar, northern Mozambique, Namibia, and south-central Tanzania.

Helium (He/2)

Description: colorless, odorless, inert gas

Uses: magnetic resonance imaging, 30%; lifting gas, 17%; analytical and laboratory applications, 14%; welding, 9%; engineering and scientific applications, 6%; leak detection and semiconductor manufacturing, 5% each; and various other minor applications, 14%.

US imports: 7 million cubic meters (2019 est.)

Import Sources (2015–18): Qatar, 79%; Canada, 8%; Algeria, 5%; Portugal, 4%; and other, 4%.

World Resources:  As of year end 2006, the total helium reserves and resources of the US were estimated to be 20.6 billion cubic meters. Helium resources of the world, exclusive of the US, were estimated in 2019 to be about 31.3 billion cubic meters (1.13 trillion cubic feet). The locations and volumes of the major deposits, in billion cubic meters, are Qatar, 10.1; Algeria, 8.2; Russia, 6.8; Canada, 2.0; and China, 1.1.

Substitutes: There is no substitute for helium in cryogenic applications if temperatures below -256°C (-429°F) are required. Argon can be substituted for helium in welding, and hydrogen can be substituted for helium in some lighter-than-air applications in which the flammable nature of hydrogen is not objectionable. Hydrogen is also being investigated as a substitute for helium in deep-sea diving applications below 305 m (1,000 ft).

Natural Rubber

Description: Natural rubber is produced from rubber trees as a latex liquid. Rubber is very useful because it is waterproof, is highly elastic, and is highly resilient.

Uses: tires and inner tubes; footwear; gasket packaging and sealing; hoses and belting

US Imports: 915,662 mt (2019)

Import Sources (2019): Indonesia, 57%; Thailand, 23%; Cote d’Ivoire, 6%; Liberia, 4%; Malaysia, 3%; Vietnam, 3%; other, 4%

World Resources: Largest producers of natural rubber are Thailand, Indonesia, Malaysia, Vietnam, India, China, Philippines, and Nigeria.

Quartz Crystal

Description: Industrial cultured quartz crystal is electronic-grade quartz crystal that is manufactured, not mined. Cultured or synthetic quartz is produced by a hydrothermal process and is used for its unique piezoelectric properties. Used in crystal oscillators within watches and clocks, signal stabilization with radio transmitters and receivers, sensor material in extremely sensitive scales, and in Global Positioning Systems (GPS).

Uses: military radios; electronic warfare; guidance systems; radar; navigation; aviation electronics

US Imports: The US Census Bureau, which is the primary government source of US trade data, does not provide import or export statistics specific to electronic and optical-grade quartz crystal.

Import Sources (2015–18): Although no definitive data exist listing import sources for cultured quartz crystal, imported material is thought to be mostly from China, Japan, Romania, and the UK.

World Resources: Limited resources of natural quartz crystal suitable for direct electronic or optical use are available throughout the world. World dependence on these resources will continue to decline because of the increased acceptance of cultured quartz crystal as an alternative material.

Substitutes: Silicon is increasingly being used as a substitute for quartz crystal for frequency-control oscillators in electronic circuits. Other materials, such as aluminum orthophosphate (the very rare mineral berlinite), langasite, lithium niobate, and lithium tantalate, which have larger piezoelectric coupling constants, have been studied and used. The cost competitiveness of these materials, as opposed to cultured quartz crystal, is dependent on the type of application that the material is used for and the processing required.

Selenium (Se/34)

Description: Selenium is a purplish-gray nonmetal semiconductor with an unusual property: its conductivity is proportional to the intensity of light shined onto it. Also, selenium can produce electricity directly from sunlight, making it useful in solar cells.

Uses: largely consumed in metallurgy and the manufacturing of glass; electrolytic manganese (selenium dioxide); lead-acid batteries; solar cells (copper indium gallium diselenide, CIGs)

US Imports: 500 mt (2019 est.)

Import Sources (2015–18): China, 22%; the Philippines, 17%; Mexico, 13%; Germany, 11%; and other, 37%.

World Resources: Reserves for selenium are based on identified copper deposits and average selenium content. Coal generally contains between 0.5 and 12 parts per million of selenium, or about 80 to 90 times the average for copper deposits. The supply of selenium is directly affected by the supply of the materials from which it is a byproduct - copper, and to a lesser extent, nickel - and it is directly affected by the number of facilities that recover selenium.

Substitutes: Silicon is the major substitute for selenium in low- and medium-voltage rectifiers. Organic pigments have been developed as substitutes for cadmium sulfoselenide pigments. Other substitutes include cerium oxide as either a colorant or decolorant in glass; tellurium in pigments and rubber; bismuth, lead, and tellurium in free machining alloys; and bismuth and tellurium in lead-free brasses. Sulfur dioxide can be used as a replacement for selenium dioxide in the production of electrolytic manganese metal, but it is not as energy efficient.

Note(s): Selenium is an essential micronutrient and is used as a human dietary supplement, a dietary supplement for livestock, and as a fertilizer additive to enrich selenium-poor soils. Selenium also is used as an active ingredient in antidandruff shampoos. Estimates for world consumption are as follows: metallurgy (including manganese production), 40%; glass manufacturing, 25%; agriculture, 10%; chemicals and pigments, 10%; electronics, 10%; and other uses, 5%.

Silicon (Si/14)

Description: Silicon is a hard and brittle crystalline solid with a blue-grey metallic luster; it is a tetravalent metalloid and semiconductor. Silicon carbide (SiC) is a synthetic mineral most commonly produced in electrical resistance furnaces by the Acheson process. A mixture of carbon material (usually petroleum coke) and either silica or quartz sand is reacted at high temperatures (1,700 – 2,500°C) resulting in the formation of α-SiC. Silicon carbide occurs in nature as the extremely rare mineral moissanite. Virtually all the silicon carbide sold in the world is synthetic. SiC has an outstanding hardness, only surpassed by diamond, cubic boron nitride, and boron carbide.

Uses: machining or finishing cast iron, non-ferrous metals, stone, leather and rubber; pressure blasting, lapping, grinding and polishing of hard metal alloys and non-metallic materials; slicing of silicon wafers; finishing and polishing of manufactured equipment; clean and shot peen jet rotor blades and other precision parts to increase resistance to fatigue failure

US Imports: Ferrosilicon – 140,000 mt; Silicon metal – 130,000 mt (2019 est.)

Import Sources (2015–18): Ferrosilicon: Russia, 38%; Canada, 13%; China, 13%; Brazil, 8%; and other, 28%. Silicon metal: Brazil, 28%; Canada, 18%; and other, 54%. Total: Russia, 20%; Brazil, 17%; Canada, 15%; and other, 48%.

World Resources: World and domestic resources for making silicon metal and alloys are abundant and, in most producing countries, adequate to supply world requirements for many decades. The source of the silicon is silica in various natural forms, such as quartzite. Excluding the US, ferrosilicon accounts for about 61% of world silicon production on a silicon-content basis. The leading countries for ferrosilicon production are, in descending order and on a contained-weight basis, China, Russia, and Norway. For silicon metal, the leading producers are China, Norway, and France. China accounted for approximately 64% of total global estimated production of silicon materials in 2019.

Substitutes: Aluminum, silicon carbide, and silicomanganese can be substituted for ferrosilicon in some applications. Gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications.

Note(s): The main consumers of silicon metal were producers of aluminum alloys and the chemical industry. The semiconductor and solar energy industries, which manufacture chips for computers and photovoltaic cells from high-purity silicon, respectively, accounted for only a small percentage of silicon demand.

Tellurium (Te/52)

Description: Tellurium is a brittle, silver-white metalloid that appears similar to tin and is mildly toxic to people. Tellurium is primarily alloyed with steel and copper to improve machining and alloyed with bismuth for thermoelectric devices.

Uses: alloying additive in steel, copper, lead, and cast iron; vulcanizing agent (rubber); thermoelectric devices; as a component of the compound Cadmium-Zinc-Telluride (CdZnTe) substrates in mid- and long-wave infrared devices; metal alloys

US Imports: 50 mt (2019 est.)

Import Sources (2015–18): Canada, 64%; China, 25%; Germany, 7%; and other, 4%.

World Resources: Data on tellurium resources is not available. More than 90% of tellurium has been produced from anode slimes collected from electrolytic copper refining, and the remainder was derived from skimmings at lead refineries and from flue dusts and gases generated during the smelting of bismuth, copper, and lead-zinc ores. Other potential sources of tellurium include bismuth telluride and gold telluride ores.

Substitutes: Several materials can replace tellurium in most of its uses, but usually with losses in efficiency or product characteristics. Bismuth, calcium, lead, phosphorus, selenium, and sulfur can be used in place of tellurium in many free-machining steels. Several of the chemical process reactions catalyzed by tellurium can be carried out with other catalysts or by means of noncatalyzed processes. In rubber compounding, sulfur and (or) selenium can act as vulcanization agents in place of tellurium. The selenides and sulfides of niobium and tantalum can serve as electrical conducting solid lubricants in place of tellurides of those metals.

Rare earth elements

Cerium (Ce/58)

Description: A very reactive iron-gray colored metal and the most abundant of the lanthanide series. Cerium averages 63 mg/kg, making it the 26th most abundant element in the earth’s crust. It is mostly used in one of its many oxide states, as the unalloyed metal is toxic and reactive.

Uses: glass manufacture additive and polishing compound; phosphors in TV screens and fluorescent lamps; chemical oxidizing agent; ceramic capacitors, semiconductors and other LCD components; wastewater treatment

US imports: Ferrocerium compounds 310 mt (2019 est.)

Import Sources (2015–18): Rare-earth compounds and metals: China, 80%; Estonia, 6%; Japan and Malaysia, 3% each; and other, 8%. Compounds and metals imported from Estonia, Japan, and Malaysia were derived from mineral concentrates and chemical intermediates produced in Australia, China, and elsewhere.

World Resources: Rare earths are relatively abundant in the Earth’s crust, but minable concentrations are less common than for most other ores. Resources are primarily in four geologic environments: carbonatites, alkaline igneous systems, ion-adsorption clay deposits, and monazite-xenotime-bearing placer deposits. Carbonatites and placer deposits are the leading sources of production of light rare-earth elements. Ion-adsorption clays are the leading source of production of heavy rare-earth elements.

Substitutes: Substitutes are available for many applications but generally are less effective.

Note(s): The estimated distribution of rare earths by end use was as follows: catalysts, 75%; metallurgical applications and alloys, 5%; ceramics and glass, 5%; polishing, 5%; and other, 10%.

Dysprosium (Dy/66)

Description: A soft metal with a bright silver luster. The metal is a by-product in the commercial production of yttrium.

Uses: permanent magnets; high-intensity lighting; capacitors and chips; data storage applications; chemical reaction testing; laser materials (ceramics and specialty glass)

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Erbium (Er/68)

Description: A bright, silvery metal. It belongs to the heavy rare earth elements that are less abundant in nature. Erbium occurs in nature in mixtures with other lanthanide elements. A common mineral is gadolinite. The metal is fairly stable in air and does not oxidize as rapidly as some other metals.

Uses: Yttrium-Aluminum-Garnet (YAG) laser applications; lasers used for cutting and welding; alloy additive for vanadium; activator for phosphors; fiber optic cables; erbium-doped optical fiber amplifiers (EDFAs)

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Europium (Eu/63)

Description: A soft silvery metal. Europium has the second lowest melting point and the lowest density of all lanthanides. It ignites in air at 150–180°C to form europium oxide and is the most reactive of the rare earth elements. The metal is soft and quite ductile. Europium is a fission product generated in nuclear reactors. Europium is not found in nature as a free element but is found mixed with other rare earth elements.

Uses: phosphors used in display screens, TVs and fluorescent lights, ceramics and specialty glass, activator for yttrium-based phosphors in TVs and computer screens, polishing powders and magnets

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Gadolinium (Gd/64)

Description: A silvery white ductile metal which is classified as a light rare earth element. It is relatively stable in dry air but tarnishes in moist air. It is ferromagnetic at temperatures below 20°C and paramagnetic above this temperature.

Uses: medical services as an MRI contrast agent and in X-ray tubes, high refractive index glass or garnets, added to chromium, iron and related alloys, high power permanent magnets, lasers, radar warning receivers and radar jammers, optical lenses, optical fibers and coatings, because Gadolinium has the highest thermal neutron capture cross-section of any known element it is used to target tumors in neutron therapy

World resources: Gadolinium is produced both from monazite and bastnasite deposits.

Note(s): Gadolinium possesses unusual metallurgical properties, to the extent that as little as 1% of gadolinium can significantly improve the workability and resistance to oxidation at high temperatures of iron, chromium, and related metals. Gadolinium as a metal or a salt absorbs neutrons and is, therefore, used sometimes for shielding in neutron radiography and in nuclear reactors. It is used as a secondary, emergency shut-down measure in some nuclear reactors.

Holmium (Ho/67)

Description: A soft, malleable metal with a bright silver luster. It oxidizes rapidly in moist air and at elevated temperatures. It falls within the heavy lanthanide rare earth elements and has the strongest magnetic moment of any natural element.

Uses: strong, artificially generated magnetic fields; red/yellow colors in glass; calibration in gamma ray spectrometers; solid state Yttrium-Iron-Garnet (YIG) and Yttrium-Lithium-Fluoride (YLF) lasers

World Resources: Holmium is found as a minor component of the minerals monazite and bastnaesite. It is extracted via ion exchange and solvent extraction from ores that are processed to extract yttrium. The main producers are China, Russia, and Malaysia.

Lanthanum (La/57)

Description: A soft, silver white metal. It is rarely kept in elemental form because it quickly oxidizes in air; it burns easily when ignited. Its oxide is much more stable and is the basis for most applications that use lanthanum.

Uses: optical fibers, glasses, and lenses; ceramic capacitors, semiconductors, and other LCD and electronic components; metal alloys for nickel metal hydride batteries; fiber-optic communication systems; samarium cobalt magnets; high-strength, low-alloy steel; infrared-absorbing glass for night vision goggles

World resources: Lanthanum is found in rare earth minerals, principally monazite (25% lanthanum) and bastnaesite (38% lanthanum). The main producers are China, Russia, and Malaysia.

Note(s): Ion-exchange and solvent extraction techniques are used to isolate rare earth elements from minerals. Lanthanum metal is usually obtained by reducing the anhydrous fluoride with calcium. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys.

Lutetium (Lu/71)

Description: A silvery white metal that is relatively stable in air. It is found in very small amounts in almost all minerals containing yttrium. Commercially extracted from monazite, it is one of the most difficult metals to prepare. It is one of the rarest and the most expensive of the rare earth metals with a price about US $10,000 per kilogram. It has very few commercial applications and is used primarily in research.

Uses: high-refractive-index optical Lutetium-Aluminum-Garnet (LuAG) lenses; X-ray phosphors; specialty silicon nitride ceramic bearings; catalyst in cracking hydrocarbons in oil refineries

World resources: In common with many other lanthanides, the main source of lutetium is the mineral monazite. It is extracted, with difficulty, by reducing the anhydrous fluoride with calcium metal. The main producers are China, Russia, and Malaysia.

Neodymium (Nd/60)

Description: A soft, bright, silvery metal. It is one of the most reactive of rare earth elements and quickly oxidizes in air. The primary source of neodymium is from carbonatites and bastnaesite, and a secondary source is in monazite. It is found in minerals such as cerite and allanite. The pure metal has limited application. A component, along with praseodymium, of didymium glass.

Uses: glass production; incandescent light bulbs; cathode ray tubes; ceramic capacitors, semiconductors, and other components for LCDs and electronics; Neodymium-Iron-Boron (NdFeB) magnets in smartphones, hard drives, other consumer electronics;  gas turbine ship propulsion

World resources: The main sources of most lanthanide elements are the minerals monazite and bastnaesite. Neodymium can be extracted from these minerals by ion exchange and solvent extraction. The element can also be obtained by reducing anhydrous neodymium chloride or fluoride with calcium. The main producers are China, Russia, and Malaysia.

Note(s): Neodymium glass is used to make lasers. These are used as laser pointers, as well as in eye surgery, cosmetic surgery and for the treatment of skin cancers. Neodymium-Iron-Boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions.

Praseodymium (Pr/59)

Description: A soft, silvery, malleable, and ductile metal. Its average concentration in earth’s crust makes it more abundant than silver, gold, or antimony. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.

Uses: doping agent in fiber optic cables and several metal alloys; thermal resistant alloys; optical lenses, filters, and coatings; ceramic capacitors, semiconductors, and other components in LCDs and electronics; Neodymium-Iron-Boron (NdFeB) high-power magnets; alloyed with magnesium in aircraft engines; lasers

World resources: Found in nature associated with other rare earth elements. Monazite and bastnaesite are the two principal commercial sources for praseodymium production, even though it is also found in apatite, trachyte, fergusonite, and eudialyte.

Samarium (Sm/62)

Description: A bright silver metal that is reasonably stable in air. Widely distributed in nature but in trace quantities always associated with other rare earth elements. The commercial source of samarium is from carbonatites and bastnaesite. It is also found in Precambrian granite rocks, shale, and in minerals such as xenotime and basalt.

Uses: Samarium-cobalt permanent magnets used in tank navigation; present in Neodymium-Yttrium-Aluminum-Garnet (NYAG) laser glass; infrared absorption glass; optical glass

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Scandium (Sc/21)

Description: Scandium is a transition metal that is silvery white, soft and light, and has historically been classified as a rare-earth element, together with yttrium and the lanthanides. It is found widely dispersed in low concentrations in many minerals, but primarily as a trace constituent of ferro magnesium minerals. The strengthening effects of scandium on aluminum alloys were discovered in the 1970s, and its use in such alloys remains its only major application.

Uses: scandium alloy in pistol frames; electronics, light aluminum-scandium alloy for aerospace components; lasers; high-intensity lamps for landing gear; solid oxide fuel cells; ceramics

US Imports: rare earth metals including Scandium 590 mt (2019 est.). The US is 100% import reliant for its scandium needs.

Import Sources (2015–18): Although no definitive data exist listing import sources, imported material is mostly from Europe, China, Japan, and Russia.

World Resources: Resources of scandium are abundant. Scandium is more abundant in the earth's crust than lead. Scandium lacks affinity for the common ore-forming anions; therefore, it is widely dispersed in the lithosphere and forms solid solutions with low concentrations in more than 100 minerals. There are identified scandium resources in Australia, Canada, China, Kazakhstan, Madagascar, Norway, the Philippines, Russia, Ukraine, and the US.

Substitutes: Titanium and aluminum high-strength alloys, as well as carbon-fiber materials, may substitute in high performance scandium-alloy applications. Light-emitting diodes displace mercury-vapor high-intensity lights in some industrial and residential applications. In some applications that rely on scandium’s unique properties, substitution is not possible.

Terbium (Tb/65)

Description: A silvery-grey rare earth metal that is malleable and ductile, soft enough to be cut with a knife, and relatively stable in air compared with other lanthanides. It is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is found in nature associated with other rare earth elements in xenotime, euxenite, cerite, monazite and gadolinite at concentrations typically < 1% rare earth oxides.

Uses: green phosphors in compact fluorescent light bulbs, LCDs, video displays and night vision goggles; additive in high-strength neodymium iron boron (NdFeB) magnets; lasers

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Thulium (Tm/69)

Description: A silvery-white, lustrous metal that is soft, malleable, and ductile. Thulium is the second-rarest element after promethium. It is very difficult to separate from the other rare earth elements and, because of its scarcity and high price, there are few applications for this element.

Uses: portable X-ray devices; ceramic magnets for microwave equipment

World resources: Found in small quantities with other rare earth elements in several yttrium-rich minerals such as xenotime, gadolinite, euxenite, loparite, fergusonite, yttroparisite, and samaskite, but extracted commercially from monazite.

Note(s): The wavelength of thulium-based lasers is very efficient for superficial ablation of tissue, with minimal coagulation depth in air or in water. This feature makes thulium lasers attractive for laser-based surgery. Thulium has been used in high-temperature superconductors similarly to yttrium

Ytterbium (Yb/70)

Description: A soft, malleable, and ductile silvery metal; its concentration in the upper continental crust is ~1.96 mg/kg. Found naturally in the minerals euxenite, gadolinite, monazite and xenotime, but it is principally commercially extracted from monazite sand that contains ~0.03% Yb.

Uses: portable X-ray machines; optical glasses, crystals, and ceramics; ytterbium lasers are used to heat treat turbine blades; super alloys for jet engines; infrared lasers

World resources: As of 2015, global reserves of rare earth elements were estimated on a rare-earth-oxide (REO) basis to be 130 million metric tons and were led by, in decreasing order of reserves, China, Brazil, Australia, and India.

Yttrium (Y/39)

Description: A soft, silver-colored metal that has similar properties to the lanthanides and is classified with the rare earth elements; its abundance in the earth’s crust is ~ 21 mg/kg, making it the 28th most abundant crustal element. Yttrium occurs with most rare earths deposits.

Uses: metallic alloy component; garnet crystals; LED phosphor for white and grey colors; optical and camera lenses; protective ceramic layers in jet engines; heat-resistant superalloys for jet engines; Yttrium-Aluminum-Garnet (YAG) and Yttrium-Iron-Garnet (YIG) laser crystals

US imports: 570 mt (2019 est.). The US is more than 95% import reliant for its yttrium needs.

Import sources (2015-2018): Yttrium compounds: China, 87%; Estonia, 5%; Republic of Korea, 2%; Japan, 2%; and other, 4%. Nearly all imports of yttrium metal and compounds are derived from mineral concentrates produced in China.

World Resources: Large resources of yttrium in monazite and xenotime are available worldwide in placer deposits, carbonatites, uranium ores, and weathered clay deposits (ion-adsorption ore). Additional resources of yttrium occur in apatite-magnetite-bearing rocks, deposits of niobium-tantalum minerals, non-placer monazite-bearing deposits, sedimentary phosphate deposits, and uranium ores.

Substitutes: Substitutes for yttrium are available for some applications but generally are much less effective. In most uses, especially in electronics, lasers, and phosphors, yttrium is generally not subject to substitution by other elements. As a stabilizer in zirconia ceramics, yttrium oxide may be substituted with calcium oxide or magnesium oxide, but the substitutes generally impart lower toughness.

Note(s): China produces most of the world’s supply of yttrium from its weathered clay, ion-adsorption ore deposits in the southern provinces - primarily Fujian, Guangdong, and Jiangxi - and from a lesser number of deposits in Guangxi and Hunan Provinces. Processing occurs primarily at facilities in Guangdong, Jiangsu, and Jiangxi Provinces. In 2019, yttrium was produced from similar clay deposits in Burma (Myanmar).