Cobalt is a metallic element that plays an outsized role in modern technology, despite its relative scarcity in the Earth’s crust. Recognized formally as an element in 1735 by Swedish chemist Georg Brandt, its compounds were used for centuries prior for their striking blue color in glazes and glass, dating back to the 3rd millennium BCE. The element was named after the German word kobold, meaning “goblin” or “evil spirit,” a term used by miners who found the ore difficult to process and noted the toxic fumes it released during smelting.
Defining the Element: Physical and Chemical Properties
Cobalt (Co) is element 27 on the periodic table, placing it among the transition metals. The pure metal is silvery-white with a faint bluish tinge, known for its hardness and durability. It is one of only three naturally occurring elements that are ferromagnetic at room temperature, meaning it can be permanently magnetized.
This ferromagnetism is stable, persisting up to a high Curie temperature of 1,121 °C, making it valuable in high-temperature applications. Cobalt typically exists with an oxidation state of +2 or +3; the +2 ion forms a characteristic pink color in aqueous solutions. Although chemically reactive, it forms a protective oxide film on its surface, granting it resistance to corrosion in air and water. The Mohs hardness scale rates cobalt at 5.0.
Global Sources and Extraction
Cobalt is rarely found in its pure metallic form, instead occurring in metallic-lustered ores such as cobaltite and erythrite. Globally, the supply is highly concentrated and recovered primarily as a byproduct of copper and nickel mining operations. The supply chain is heavily dominated by the Central African Copperbelt, particularly the Democratic Republic of Congo (DRC), which accounts for a significant portion of global production.
Other producing regions include Russia, Australia, and Canada. Industrial extraction involves crushing the ore, followed by leaching with sulfuric acid, solvent extraction, and then electrowinning to yield the refined metal. The concentration of production in the DRC and the reliance on byproduct recovery create a sensitive market vulnerable to geopolitical and economic disruptions.
Essential Roles in Modern Technology
Cobalt’s unique characteristics make it indispensable across several high-technology sectors. Its most prominent application is in rechargeable lithium-ion batteries, where it is a fundamental component of the cathode material. Cobalt’s presence, such as in lithium cobalt oxide (LCO) batteries, increases the battery’s energy density and ensures thermal stability. This stability prevents the cathode structure from collapsing during charge and discharge cycles, enhancing safety and extending the battery’s lifespan in devices like smartphones and electric vehicles.
Beyond battery technology, cobalt is a foundational element in superalloys used in high-performance machinery. These superalloys (containing 5% to 20% cobalt) are valued for their exceptional strength and resistance to heat. This makes them essential for components in jet engines, gas turbines, and aerospace applications that operate under extreme temperatures and stress. Cobalt’s ability to maintain structural integrity at temperatures up to 1,200 °C is a distinct advantage.
Cobalt compounds are also used as pigments, with cobalt blue being one of the most stable and vibrant blue colors known. Cobalt silicate and cobalt(II) aluminate impart this deep blue to glass, ceramics, and paints. Cobalt is also used as a binder in cemented carbides—hard, wear-resistant materials used for cutting and drilling tools. Its magnetic properties find use in permanent magnets for generators and motors.
Cobalt in Biology and Human Health
Cobalt is an essential trace element for human health, but only when incorporated into a specific organic molecule. Its sole biological function is as the central metal atom in Vitamin B12 (cobalamin). This vitamin is necessary for the proper functioning of the nervous system and the formation of red blood cells. The body cannot use free cobalt ions; it relies on pre-formed Vitamin B12, obtained through the consumption of animal products.
While cobalt is necessary in trace amounts, exposure to high levels of inorganic cobalt can lead to toxicity. Occupational exposure through the inhalation of cobalt dust in industrial settings (such as mining or tool manufacturing) can cause severe chronic lung problems. Long-term absorption of excess cobalt can harm the heart muscle, potentially leading to toxic cardiomyopathy. In rare cases, the wear of metal-on-metal hip implants can release cobalt particles into the bloodstream, resulting in systemic toxicity symptoms like nerve damage and thyroid dysfunction.