Magnesium comes from two broad categories of sources: solid mineral deposits mined from the earth’s crust and dissolved salts extracted from brines and seawater. The mineral magnesite and the rock dolomite supply most of the world’s mined magnesium ore, while salt lakes and ocean water serve as enormous liquid reserves. Once the raw material is in hand, turning it into usable metal involves either extreme heat (thermal reduction) or running electrical current through molten salts (electrolysis), each with distinct trade-offs in energy use and environmental footprint.
Where Magnesium Deposits Occur
Magnesium is the eighth most abundant element in the earth’s crust and the third most abundant dissolved element in seawater, so the raw material itself is not scarce. The challenge has always been concentrating and extracting it economically. Commercially relevant deposits fall into a few geological categories. Magnesite, the primary ore mineral, forms in settings tied to ultramafic and carbonate-rich rocks. Research on magnesium carbonate formation identifies at least five distinct geological settings where these minerals concentrate: veins hosted in ultramafic rock, the matrix of carbonated peridotite, soil nodules, alkaline lake and playa deposits, and diagenetic replacements within older carbonate rocks like limestone and dolostone.1PubMed Central. Formation of Magnesium Carbonates on Earth and Implications for Mars
Dolomite, a calcium-magnesium carbonate rock, is even more widespread than magnesite and serves as a feedstock for many thermal reduction plants. China holds the world’s largest magnesite reserves and dominates global magnesium metal production, accounting for roughly 85 percent of output in most recent years. Other countries with meaningful deposits include Russia, Brazil, Turkey, Australia, North Korea, and Austria. The United States has limited magnesite mining but historically produced significant magnesium from seawater, a practice that peaked in the mid-twentieth century.
Open-Pit Mining and Ore Beneficiation
Most magnesite is extracted through conventional open-pit or underground mining, depending on how deep the deposit sits. The raw ore that comes out of the ground is rarely pure enough to feed directly into a smelter. It contains impurities like silica, calcium-bearing minerals such as dolomite, quartz, and chlorite that must be reduced before processing. A range of techniques exist to clean up magnesite ore, including magnetic separation, thermal sorting, chemical treatment, and electrical separation, but froth flotation is the most commonly used method worldwide.2PubMed Central. Removal of Silicon from Magnesite by Flotation: Influence of Particle Size and Mechanical Mechanism
Flotation works by exploiting differences in how water interacts with mineral surfaces. The crushed ore is mixed into a slurry with water and chemical agents called collectors. Particles of the desired mineral become water-repellent, attach to air bubbles, and float to the surface as a froth that gets skimmed off. The unwanted gangue minerals stay behind in the liquid. Researchers continue to refine this technique in two directions: reverse flotation, which removes silica from the magnesite concentrate, and direct flotation, which targets calcium-containing impurities like dolomite.3PubMed Central. Comparative Analysis of Industrial Fused Magnesia from Natural and Flotation-Processed Magnesite: Associations Among CaO/SiO 2 Ratio, Silicate Phase Formation, and Microcracking The ratio of calcium oxide to silica in the final product matters a great deal for downstream uses, particularly for refractory-grade magnesia used to line furnaces and kilns.
The Pidgeon Process and Thermal Reduction
The dominant method for producing metallic magnesium worldwide is the Pidgeon process, a thermal reduction technique developed in the 1940s. It accounts for the vast majority of magnesium smelting, especially in China, where cheap labor, abundant dolomite, and access to ferrosilicon have made it the default approach for decades. The basic idea is straightforward: calcined dolomite (dolomite that has been roasted to drive off carbon dioxide, leaving behind a mix of magnesium oxide and calcium oxide) is mixed with ferrosilicon, a silicon-iron alloy that acts as the reducing agent. This mixture is pressed into pellets and loaded into retorts, which are essentially large steel tubes.
The retorts are heated to around 1,200 degrees Celsius under a high vacuum of about 10 pascals. At that temperature and pressure, silicon strips the oxygen from magnesium oxide, and magnesium comes off as a vapor. The vapor condenses at the cooler end of the retort into crystalline crowns of relatively pure metal, which are then remelted and cast into ingots.4PubMed Central. Novel Efficient Reduction Route for Magnesium Production Using Silicothermic Process
For all its simplicity, the Pidgeon process is an energy hog. Each ton of magnesium produced requires roughly 8.7 tons of coal equivalent in total energy and generates about 26 tons of greenhouse gas emissions, making it one of the more carbon-intensive metals to produce.5Journal of Magnesium and Alloys. Comparative evaluation of energy and resource consumption for vacuum carbothermal reduction and Pidgeon process used in magnesium production The process also suffers from a long production cycle and batch-mode operation. Each retort run takes many hours, and the retorts themselves degrade quickly at such extreme temperatures and need frequent replacement. These drawbacks have prompted considerable research into alternatives, including vacuum carbothermal reduction, which replaces the expensive ferrosilicon with cheaper carbon-based reductants and aims to cut both energy use and cost.6PubMed Central. Research on the Process, Energy Consumption and Carbon Emissions of Different Magnesium Refining Processes
Electrolytic Extraction
The other major route to metallic magnesium is electrolysis, which was actually the original industrial method and is still used by producers outside China. In this process, magnesium chloride (derived from brines, seawater, or mineral sources) is dissolved in a molten salt bath and an electric current is passed through it. Magnesium metal collects at the cathode and chlorine gas is released at the anode.
Electrolytic production tends to have a lower carbon footprint per ton of metal than the Pidgeon process, particularly when the electricity comes from hydropower or other clean sources. Norway, Israel, and historically the United States and Canada have all operated electrolytic magnesium plants. The trade-off is higher capital cost: the cells, anodes, and chlorine-handling systems are expensive to build and maintain, and the process demands very pure magnesium chloride feed to avoid contaminating the bath.
One active area of research aims to make electrolysis cheaper and more efficient by changing the anode chemistry. A recent study demonstrated a novel approach using argon plasma as the anode in molten chloride electrolysis. The ionized argon actively participates in the reaction, making the oxidation of chloride ions to chlorine gas thermodynamically spontaneous rather than requiring external energy to drive it.7PubMed Central. Towards green magnesium preparation using a recyclable argon plasma anode for continuous electrolysis in molten chlorides If scalable, approaches like this could shift the economics back in favor of electrolysis and reduce the industry’s reliance on the high-emission thermal route.
Magnesium from Brines and Seawater
Not all magnesium comes from rock. Salt lakes, underground brines, and even the ocean itself contain dissolved magnesium in concentrations high enough to extract commercially. The Dead Sea, the Great Salt Lake in Utah, and various salt lakes on China’s Qinghai-Tibet Plateau are among the most significant brine sources. Seawater contains about 1.3 grams of magnesium per liter, which sounds dilute but adds up to a functionally unlimited reserve given the volume of the oceans.
Extracting magnesium from brine typically involves precipitating it as magnesium hydroxide (brucite) or magnesium chloride through chemical treatment, then feeding the result into either the thermal or electrolytic pathway. One newer approach targets salt lake brines using extraction-electrodeposition technology, achieving extraction efficiencies around 61 percent for magnesium ions at concentrations typical of concentrated brines.8Separation and Purification Technology. Separation and production of metallic magnesium from salt lake brine by extraction-electrodeposition technology
Desalination plants are also becoming a potential magnesium source. The concentrated reject brine left over after producing drinking water from seawater is rich in magnesium. Research has shown that roughly 55 percent of magnesium can be recovered from nanofiltration brine and about 65 percent from reverse osmosis brine under optimized conditions, with full recovery achievable at higher pH levels when the right alkaline reagent ratio is used.9Journal of Environmental Chemical Engineering. Magnesium recovery from brackish water desalination brine and valorization in fertilizer production This “waste-to-resource” approach is particularly appealing in water-scarce regions that already operate large desalination facilities, because it turns a disposal problem into a revenue stream.
Non-Metallic Magnesium Products
A large share of mined magnesium minerals never becomes metallic magnesium at all. Instead, the ore is processed into industrial compounds used across a surprisingly wide range of industries. Calcined magnesite, produced by roasting the ore at moderate temperatures, becomes magnesia (magnesium oxide), which is the workhorse refractory material for steelmaking furnaces and cement kilns because it withstands extremely high temperatures without melting. Dead-burned magnesia, heated even further, is denser and more chemite-resistant, and goes into the bricks lining basic oxygen furnaces.
Dolomite follows a similar path. When calcined at temperatures around 1,200 degrees Celsius, it yields a mix of reactive calcium and magnesium oxides totaling over 50 percent of the product by weight, though that reactivity drops sharply at higher calcination temperatures.10PubMed Central. Phosphate Cements Based on Calcined Dolomite: Influence of Calcination Temperature and Silica Addition Calcined dolomite finds use in construction materials, water treatment, agriculture (as a soil amendment to raise pH), and as a flux in iron and steel production.
Other non-metallic magnesium products include magnesium sulfate (Epsom salt), magnesium hydroxide (the active ingredient in milk of magnesia and a flame retardant), and magnesium carbonate (used as a drying agent by gymnasts and rock climbers, among other applications). These products are typically manufactured from mined minerals through relatively simple chemical reactions rather than the energy-intensive metal smelting routes described above.
What Metallic Magnesium Is Used For
Once metallic magnesium is produced, it gets alloyed with aluminum, zinc, and other elements to create materials prized for their low density. Magnesium alloys are roughly a third lighter than aluminum alloys and about 75 percent lighter than steel, making them especially attractive in transportation. The automotive industry has steadily increased its use of magnesium alloy parts over the past two decades, applying them across body systems, chassis components, powertrain housings, and interior and exterior trim.11Journal of Magnesium and Alloys. Development and application of magnesium alloy parts for automotive OEMs: A review Steering column brackets, instrument panel beams, and transmission cases are common examples.
Beyond cars, magnesium alloys show up in aerospace components, laptop and phone casings, power tools, and medical implants. Magnesium’s biocompatibility and ability to gradually dissolve inside the body have made it a subject of intense research for biodegradable surgical screws and stents. The metal also plays a niche but important role as a desulfurization agent in steelmaking and as a sacrificial anode to protect steel pipelines and ship hulls from corrosion.
Recycling Magnesium Scrap
Given the enormous energy required to produce primary magnesium, recycling makes both economic and environmental sense. Magnesium scrap from manufacturing trimmings, end-of-life vehicles, and electronics can be remelted to recover the metal. The process is not as simple as tossing scrap into a furnace, though. Many magnesium parts arrive coated with paint, anodized layers, or other surface treatments that introduce impurities into the melt if not removed first.
Research into chemical de-coating has shown that stripping these surface layers before remelting significantly improves the quality of the recycled ingot. When coated scrap is remelted without cleaning, the resulting metal has higher density and hardness than properly de-coated material, indicating that paint residues and other contaminants are getting incorporated into the metal matrix.12Metallurgical and Materials Engineering. Recycling of Magnesium Alloy Scrap by Remelting and Chemical De-coating Process Using a sodium chloride flux layer during remelting helps trap some impurities, but pre-cleaning remains the more effective route to high-purity recycled magnesium. The recycling rate for magnesium is still well below that of aluminum, partly because mixed alloy scrap is harder to sort and partly because the small volumes used per vehicle have historically made collection less economical.
Fire Hazards in Processing and Handling
Magnesium’s reactivity, the same property that makes it useful as a desulfurization agent and sacrificial anode, also makes it genuinely dangerous in certain forms. Fine magnesium dust and chips can ignite easily, and magnesium fires burn at extremely high temperatures and are difficult to extinguish with conventional methods. Water, in fact, makes things worse: when magnesium reacts with water, it produces hydrogen gas, which is highly flammable and can intensify fire spread and combustion. At the same time, the presence of water vapor can break down the thin protective oxide layer on magnesium surfaces, making the underlying metal more vulnerable to ignition in the first place.13Fuel. Effect of moisture content on the fire hazard of magnesium metal layers
This creates a somewhat counterintuitive safety picture. A small amount of moisture on magnesium dust initially seems to help by cooling through evaporation and reducing ignition sensitivity. But once a fire starts, the moisture-driven hydrogen generation makes the fire burn harder. The effect is more pronounced with fine dust than with larger chips, because the greater surface area of fine particles allows faster reaction with water vapor. Industrial facilities that process magnesium powder go to considerable lengths to keep the environment dry and to use specialized extinguishing agents, typically dry sand or Class D fire extinguishers, rather than water or standard foam.
The Environmental Equation and Emerging Alternatives
The environmental cost of magnesium production is dominated by the Pidgeon process and its appetite for fossil fuels. A life-cycle assessment of the major production technologies confirms what plant-level data suggest: both thermal and electrolytic processes carry significant environmental burdens, but the thermal route is particularly carbon-heavy because it relies on coal or natural gas not only for the reduction reaction itself but also to calcine the dolomite feedstock and maintain the retort temperatures.14Resources, Conservation and Recycling. LCA of magnesium production: Technological overview and worldwide estimation of environmental burdens The roughly 26 tons of greenhouse gas emissions per ton of magnesium metal produced via the Pidgeon process puts it in unflattering company among structural metals.5Journal of Magnesium and Alloys. Comparative evaluation of energy and resource consumption for vacuum carbothermal reduction and Pidgeon process used in magnesium production
Several strategies are in various stages of development to bring that number down. Vacuum carbothermal reduction replaces ferrosilicon with carbon, cutting raw material costs and potentially allowing continuous rather than batch operation. Electrolytic processes powered by renewable electricity could produce magnesium with a fraction of the thermal route’s emissions, and the argon plasma anode research mentioned earlier hints at ways to reduce the electricity needed per ton. Brine and seawater extraction avoid mining altogether and pair well with electrolytic production. And of course, better recycling infrastructure would reduce demand for primary production.
China’s dominance in magnesium production also creates supply-chain concentration risk that other countries have begun to take seriously. When China briefly restricted magnesium exports in late 2021, prices on the European spot market spiked by several hundred percent within weeks, exposing how dependent the global aluminum and automotive industries had become on a single source. That episode accelerated interest in reopening or developing domestic production capacity in North America, Europe, and Australia, with several projects now at various stages of permitting and construction. Whether those projects ultimately use thermal or electrolytic methods, and whether they can compete on cost with Chinese Pidgeon-process metal, will shape the geography of magnesium production for the next generation.