Critical Minerals Glossary - Critical and Strategic Metals Hub

This glossary provides definitions for the most commonly encountered terms in the critical and strategic minerals field. Whether you are new to the sector or looking for a quick reference on a specific concept, these definitions are designed to be both accessible and technically accurate. Terms are organized alphabetically, and each entry provides sufficient context to be useful as a standalone reference.

Alloy: A metallic substance composed of two or more elements, at least one of which is a metal. Alloys are engineered to achieve specific properties such as increased strength, corrosion resistance, or conductivity that the individual constituent metals do not possess on their own. Common examples include steel (iron and carbon), brass (copper and zinc), and superalloys used in jet engines.

Beneficiation: The initial processing of mined ore to increase the concentration of the target mineral or metal. Beneficiation typically involves physical processes such as crushing, grinding, screening, magnetic separation, and flotation to separate valuable minerals from waste rock (gangue). The output is a concentrate with a higher grade than the original ore, suitable for further refining.
Byproduct: A mineral or metal that is recovered during the extraction or processing of a different primary commodity. Many critical minerals, including cobalt, indium, gallium, and germanium, are predominantly or exclusively produced as byproducts of copper, zinc, aluminum, or coal processing. Byproduct dependency creates unique supply vulnerabilities because production volumes are tied to the economics of the primary commodity rather than demand for the byproduct itself.

Cathode: The positive electrode in an electrochemical cell such as a battery. In the context of critical minerals, cathode chemistry is a primary driver of demand for materials like lithium, nickel, cobalt, and manganese. Common cathode types in lithium-ion batteries include NMC (nickel-manganese-cobalt), NCA (nickel-cobalt-aluminum), and LFP (lithium iron phosphate), each with different mineral requirements and performance characteristics.
Concentrate: The product of the beneficiation process, consisting of ore that has been processed to increase the proportion of the target mineral. Concentrates are typically sold to smelters or refineries for further processing into pure metals or chemical compounds. The grade of a concentrate, expressed as a percentage of the target metal, varies by mineral and processing method.
Critical Mineral: A mineral or element that is deemed essential to economic prosperity or national security and whose supply chain is vulnerable to disruption. Designations vary by jurisdiction, as each country assesses criticality based on its own economic needs, import dependencies, and geopolitical considerations. The United States, European Union, Australia, Canada, Japan, and other nations each maintain their own official critical minerals lists, which are periodically revised.

Downstream: The later stages of a mineral supply chain, encompassing refining, manufacturing of components, and production of finished goods. In the critical minerals context, downstream processing includes the production of battery-grade chemicals, permanent magnets, semiconductor wafers, and other intermediate products. Downstream capacity is often more geographically concentrated than mining, with China dominating many downstream segments.

E-waste: Discarded electronic and electrical equipment, including smartphones, computers, televisions, batteries, and circuit boards. E-waste is a significant potential source of secondary critical minerals through recycling, containing recoverable quantities of gold, silver, copper, palladium, platinum, cobalt, lithium, rare earth elements, and other valuable materials. Also referred to as waste electrical and electronic equipment (WEEE).

Flotation: A widely used beneficiation process in which ground ore is mixed with water and chemical reagents to create a slurry. Air is introduced to create bubbles, and hydrophobic mineral particles attach to the bubbles and rise to the surface as a froth, which is collected as concentrate. Flotation is the primary method for concentrating sulfide ores of copper, lead, zinc, and nickel, and is also used for some non-sulfide minerals.
Friendshoring: A trade and industrial strategy in which a country seeks to concentrate supply chain relationships among geopolitically aligned or trusted partner nations. In the critical minerals context, friendshoring involves developing mining, processing, and manufacturing capacity within allied countries to reduce dependence on geopolitical rivals, particularly China. Key friendshoring initiatives include the Minerals Security Partnership and bilateral agreements between the United States, Australia, Canada, the European Union, Japan, and South Korea.

Gangue: The commercially worthless rock and minerals that surround or are intermixed with the target ore minerals in a deposit. Gangue must be separated from valuable minerals during beneficiation. The nature and quantity of gangue material affects processing costs, reagent requirements, and the environmental footprint of mining operations. Common gangue minerals include quartz, feldspar, and calcite.
Grade: The concentration of a target mineral or metal within an ore body, typically expressed as a percentage by weight, grams per tonne (g/t), or parts per million (ppm). Higher-grade deposits are generally more economical to mine, though other factors such as deposit size, location, mining method, and mineralogy also affect viability. Declining ore grades worldwide for many critical minerals are a significant concern for future supply security.

Hydrometallurgy: A branch of metallurgy involving the use of aqueous solutions to extract and recover metals from ores, concentrates, or recycled materials. Hydrometallurgical processes include leaching, solvent extraction, ion exchange, and electrowinning. Hydrometallurgy is increasingly important for processing laterite nickel ores, recovering cobalt and lithium from batteries, and extracting rare earth elements. It generally operates at lower temperatures than pyrometallurgy and can be more selective.

In-situ Recovery: A mining technique in which minerals are extracted from an ore body without conventional excavation. A leaching solution is injected into the deposit through boreholes, dissolving the target minerals, and the pregnant solution is pumped to the surface for processing. In-situ recovery, also called in-situ leaching or solution mining, is commonly used for uranium and is being developed for copper and other metals. It has a smaller surface footprint than open-pit or underground mining.

Laterite: A type of soil or rock rich in iron and aluminum oxides, formed through intense weathering in tropical and subtropical climates. Laterite deposits are a major source of nickel and cobalt, particularly in Indonesia, the Philippines, and New Caledonia. Laterite ores are typically processed using hydrometallurgical methods such as high-pressure acid leaching (HPAL) or through pyrometallurgical smelting to produce ferronickel or nickel pig iron.
Leaching: A hydrometallurgical process in which a solvent, typically an acid or alkaline solution, is applied to ore or concentrate to dissolve and extract the target metal. Leaching can be performed in various configurations including heap leaching (stacking ore on lined pads and irrigating with solution), tank leaching (submerging ore in vats of solution), and in-situ leaching (injecting solution into underground deposits). The resulting metal-bearing solution is then processed to recover the dissolved metals.

Metallurgy: The science and technology of metals, encompassing the extraction of metals from their ores, the development and production of metallic alloys, and the shaping and treatment of metals for practical use. Metallurgy is broadly divided into extractive metallurgy (getting metals from ores), physical metallurgy (the properties and behavior of metals), and process metallurgy (industrial-scale metal production). Pyrometallurgy and hydrometallurgy are the two primary branches of extractive metallurgy.
Midstream: The intermediate stages of a mineral supply chain between mining and end-use manufacturing. Midstream activities include smelting, refining, chemical processing, and the production of intermediate products such as battery-grade chemicals, metal powders, and precursor materials. Control of midstream capacity is a key factor in critical mineral supply chain security.

Offtake Agreement: A contractual arrangement between a mineral producer and a buyer in which the buyer commits to purchasing a specified quantity of the producer's output over a defined period, often before the mine or processing facility is operational. Offtake agreements provide revenue certainty for producers, which helps secure project financing, while guaranteeing supply for buyers. They are a common mechanism in the critical minerals sector and play a significant role in determining trade flows.
Ore: A naturally occurring solid material from which a metal or valuable mineral can be extracted profitably. The distinction between ore and ordinary rock is economic as much as geological. A deposit becomes ore when the concentration of the target mineral, combined with prevailing commodity prices and available extraction technology, makes mining commercially viable. Changes in price, technology, or regulation can cause material previously considered waste to become ore, and vice versa.

PGM (Platinum Group Metals): A group of six chemically similar metallic elements: platinum, palladium, rhodium, ruthenium, iridium, and osmium. PGMs are characterized by exceptional catalytic properties, high melting points, and resistance to corrosion. Their primary applications include automotive catalytic converters, industrial catalysts, electronics, jewelry, and hydrogen fuel cells. South Africa and Russia together account for the vast majority of global PGM production.
Pyrometallurgy: A branch of extractive metallurgy that uses high temperatures to extract and refine metals from ores and concentrates. Pyrometallurgical processes include roasting, smelting, converting, and fire refining, typically involving furnaces operating at temperatures from several hundred to over 1,500 degrees Celsius. Pyrometallurgy is widely used for copper, nickel, lead, zinc, and tin extraction. While energy-intensive, it can process a wide range of feed materials and achieves high recovery rates.

Rare Earth Element (REE): A group of 17 chemically similar metallic elements comprising the 15 lanthanides (lanthanum through lutetium) plus scandium and yttrium. Despite their name, most rare earth elements are relatively abundant in the Earth's crust but rarely occur in concentrated, economically exploitable deposits. REEs are subdivided into light rare earths (lanthanum through europium) and heavy rare earths (gadolinium through lutetium plus yttrium). They are essential for permanent magnets, catalysts, phosphors, glass polishing, and numerous high-technology applications.
Refining: The process of purifying a crude metal or intermediate product to meet specifications required for commercial or industrial use. Refining can involve electrolytic processes (electrorefining), chemical processes (solvent extraction, precipitation), or thermal processes (zone refining, vacuum distillation). The output is typically a high-purity metal or chemical compound. Refining capacity for many critical minerals is heavily concentrated in China, creating significant supply chain risks.
Reserve: The portion of a measured or indicated mineral resource that has been demonstrated to be economically and technically feasible to extract under current conditions. Reserves represent the subset of known mineral deposits that can be mined profitably using existing technology at prevailing prices, taking into account all legal, environmental, and regulatory requirements. Reserve estimates are more conservative and commercially significant than resource estimates.
Resource: A concentration of minerals in a form that has reasonable prospects for eventual economic extraction. Resources are classified by increasing geological confidence as inferred, indicated, or measured. A mineral resource is a broader category than a reserve, as it includes material that may not be economically viable to extract under current conditions but could become viable with changes in price, technology, or other factors.
Resource Nationalism: The tendency of governments to assert greater control over natural resource extraction within their borders, often through measures such as increased taxation, export restrictions, mandatory domestic processing requirements, nationalization of mining assets, or renegotiation of existing contracts. Resource nationalism can significantly affect critical mineral supply chains by restricting exports, increasing costs, or creating uncertainty that deters investment. Recent examples include Indonesia's nickel ore export ban and China's restrictions on gallium and germanium exports.

Smelting: A pyrometallurgical process that uses heat and a chemical reducing agent to decompose an ore or concentrate and extract the base metal. During smelting, the metal oxide is reduced to its metallic form while impurities combine with a flux to form a slag, which is separated and removed. Smelting is a key step in the production of copper, nickel, lead, zinc, tin, and other base metals. Modern smelters are large, capital-intensive facilities that require reliable access to concentrates and energy.
Strategic Mineral: A mineral or metal that is essential for national defense, military applications, or the strategic economic interests of a nation. While the terms critical and strategic are sometimes used interchangeably, strategic minerals are specifically associated with defense and security considerations. Examples include tungsten (used in armor-piercing ammunition), titanium (aerospace structures), and rare earth elements (precision-guided munitions, radar systems). National stockpiling programs typically focus on strategic minerals.
Superalloy: A high-performance alloy designed to maintain its mechanical strength, surface stability, and resistance to creep and oxidation at elevated temperatures, typically above 700 degrees Celsius. Superalloys are based on nickel, cobalt, or iron and frequently contain critical minerals including rhenium, hafnium, tantalum, and tungsten. Their primary applications include gas turbine engines for aviation and power generation, where they are used in the hottest sections of the engine.

Tailings: The residual waste material remaining after the economically valuable minerals have been extracted from ore during processing. Tailings are typically a slurry of finely ground rock, water, and process chemicals that is deposited in purpose-built tailings storage facilities. The management and long-term stability of tailings storage is a significant environmental and safety concern in the mining industry. Some historical tailings deposits are now being re-evaluated as potential sources of critical minerals as extraction technologies improve.

Upstream: The early stages of a mineral supply chain, encompassing exploration, mine development, and the extraction of ore from the ground. Upstream activities are the foundation of the mineral supply chain and are influenced by geological factors, regulatory environments, environmental and social considerations, and commodity prices. Upstream investment decisions made today determine the supply available years or decades in the future, making the sector inherently cyclical.
Urban Mining: The process of recovering valuable materials, including critical minerals, from manufactured products, buildings, and waste streams rather than from geological deposits. Urban mining encompasses the recycling of e-waste, spent batteries, catalytic converters, industrial scrap, and other end-of-life products. As primary ore grades decline and concerns about supply security increase, urban mining is becoming an increasingly important component of critical mineral supply strategies.

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