Magnesium (Mg) is an alkaline earth metal recognized as the lightest structural metal, making it invaluable for modern industry. Its lightweight nature and high strength-to-weight ratio lead to heavy use in alloys for the automotive, aerospace, and electronics sectors. Magnesium compounds are also used extensively in medicine, agriculture, and chemical production. The global supply of this versatile metal relies on a complex supply chain that begins in specific geographic locations and involves distinct processing methods to convert raw sources into usable metal.
Global Centers of Magnesium Production
Primary magnesium metal production is highly concentrated geographically, with a single nation dominating the global market. The vast majority of the world’s primary magnesium, typically over 85%, originates from China. This market dominance is a relatively recent phenomenon, shifting from a period where Western nations were the primary suppliers using electrolytic methods.
Within China, production is heavily concentrated in the central provinces of Shaanxi and Shanxi, which possess the necessary raw materials and energy infrastructure. The city of Yulin in Shaanxi province is a particularly significant hub, and China’s output far exceeds the combined total of all other producing nations.
The next largest producers, such as Russia and Israel, account for a small fraction of the total world output. Russia utilizes its extensive mineral resources, while Israel extracts magnesium from the highly concentrated brines of the Dead Sea. This geopolitical concentration means that global supply chains are heavily reliant on the stability of just a few key regions.
Primary Natural Sources of Magnesium
The industrial process for obtaining magnesium metal begins with three main types of raw sources: solid minerals, inland brines, and seawater. The most commonly mined mineral sources are magnesite (\(\text{MgCO}_3\)) and dolomite (\(\text{MgCO}_3 \cdot \text{CaCO}_3\)). These carbonate-based ores are abundant in many regions and serve as the primary feedstock for the dominant production method.
These mineral sources must first be subjected to a high-temperature process called calcination, which removes water and carbon dioxide (\(\text{CO}_2\)). This converts the magnesium carbonate into magnesium oxide (\(\text{MgO}\)), often called magnesia, which is the reactive compound needed for metal extraction. The location of suitable deposits is a major factor in determining where production facilities are sited.
Alternatively, magnesium can be extracted from brines, which are highly concentrated salt solutions, or from the vast reserves of seawater. These liquid sources contain magnesium primarily in the form of magnesium chloride (\(\text{MgCl}_2\)). While seawater is an almost limitless source, processing it is generally more energy-intensive than utilizing concentrated brines or mined ores.
Conversion Processes for Usable Magnesium
The raw magnesium compounds are converted into purified metal using one of two primary industrial methods: the Pidgeon process or the electrolytic process. The Pidgeon process, a thermal reduction method, is the dominant technique used in China, powering the majority of the world’s supply. This method involves mixing calcined dolomite (\(\text{MgO} \cdot \text{CaO}\)) with a reducing agent, typically ferrosilicon (\(\text{FeSi}\)).
The mixture is heated to high temperatures, often between 1373 to 1553 Kelvin, in a vacuum retort. This process causes the ferrosilicon to reduce the magnesium oxide, driving off pure magnesium vapor which then condenses outside the reaction zone. The Pidgeon process is popular because it is less complex technologically and requires lower capital investment, making it cost-effective despite its high energy consumption and greenhouse gas emissions.
The second major method is the electrolytic process, which was historically dominant outside of China and is still used by a few global producers, such as those drawing from Dead Sea brines. This process uses an electrical current to separate molten, anhydrous magnesium chloride (\(\text{MgCl}_2\)) into magnesium metal and chlorine gas (\(\text{Cl}_2\)). While the preparation of the anhydrous \(\text{MgCl}_2\) feedstock is energy-intensive, the overall process is often more energy-efficient and generates lower carbon emissions than the Pidgeon process.