The Swedish chemist Georg Brandt identified cobalt as a distinct metallic element around 1735, making it the first metal whose discovery can be attributed to a single named individual rather than to anonymous ancient metallurgists. But cobalt compounds had been coloring glass and ceramics a vivid blue for more than three thousand years before Brandt figured out what was actually causing the color. The gap between human use of cobalt and its formal identification as an element is one of the longest in chemistry, and the story of how that gap closed involves folklore, frustrated miners, and a persistent scientific detective.
Thousands of Years of Blue Before Anyone Knew Why
Long before anyone had a concept of chemical elements, artisans prized certain minerals for the intense blue they produced in glass and glazes. The earliest confirmed use of cobalt-blue colorants in ancient Egypt dates to the middle of the 18th Dynasty, during the reign of King Tuthmosis III, roughly 1479 to 1424 BC. The source of the pigment was almost certainly cobaltiferous alum from oases in the Egyptian Western Desert, and the resulting deep-blue glass became common at major workshops such as those at Malkata and Amarna by the 14th century BC.1Journal of Archaeological Science. Transition in the use of cobalt-blue colorant in the New Kingdom of Egypt Chinese potters were producing cobalt-blue ceramics centuries before Europeans, and Persian artisans used cobalt glazes extensively in their tilework during the medieval period.
Throughout all of this, nobody understood that the blue came from a specific metallic element. Craftspeople knew which mineral deposits produced the color and how to prepare them, but the concept of an element did not yet exist. The blue was simply a property of certain earths and stones. This practical mastery without theoretical understanding is characteristic of pre-modern chemistry, but cobalt’s case is extreme: the pigment was in continuous use for over three millennia before anyone isolated the metal responsible.
Kobolds in the Mines
The word “cobalt” itself carries a trace of the confusion that surrounded the element before its discovery. In the mining districts of the Erzgebirge mountains, which straddle the border between modern Germany and the Czech Republic, miners had long encountered ores that looked like they should contain valuable silver or copper but stubbornly refused to yield either. Worse, smelting these ores often released toxic arsenic fumes that sickened the workers. The miners blamed these troublesome rocks on Kobolds, mischievous underground spirits from German folklore, and named the ores accordingly.
What the miners were actually encountering were cobalt arsenide minerals such as smaltite and cobaltite. These ores contain arsenic alongside the cobalt, which explains both the poisonous fumes during smelting and the failure to extract the expected silver. The “cursed” reputation of cobalt ores persisted for centuries, even as glassmakers in the same region were happily using the blue pigment derived from them. The disconnect is striking: the same mineral that miners considered a dangerous nuisance was, in processed form, a prized commodity in the glass and ceramics trade. By the 16th century, cobalt-colored glass was being ground into a fine blue painting pigment called smalt, which required the development of new preparation procedures beyond simple glassmaking.2Archaeological and Anthropological Sciences. Co-glass and blue pigment smalt production at the turn of the 15th/16th centuries: LA-ICP-MS study
Georg Brandt and the Isolation of Cobalt
Georg Brandt was born in 1694 in Riddarhyttan, Sweden, the son of a mining and smelting operator. He studied chemistry and medicine at several European universities before returning to Sweden and taking charge of the chemical laboratory at the Bureau of Mines in Stockholm. His professional life was deeply tied to the practical problems of mining and metallurgy, which put him in an ideal position to investigate the troublesome cobalt ores that had vexed miners for generations.
By the early 1730s, Brandt had begun a systematic study of the blue pigment known as zaffer (or zaffre), which was produced from cobalt-bearing ores and widely used in the glass and ceramics industries. The prevailing belief at the time was that the blue color came from bismuth, iron, or copper mixed into the mineral. Brandt’s key insight, published around 1735 and expanded in subsequent papers, was that the blue was caused by a previously unrecognized “semi-metal” that was distinct from all known metals. He showed that the substance he isolated from the ore had unique properties: it was magnetic, it produced a characteristic blue color in glass, and it could not be reduced to any combination of already-known metals. He called this new substance “cobalt rex,” later shortened simply to cobalt.
Brandt’s claim was not universally accepted at first. Several prominent chemists argued that his “new” metal was simply a form of iron or bismuth, since cobalt shared some superficial properties with both. It took decades of further work by other chemists, including Torbern Bergman in the 1780s, to fully establish cobalt’s credentials as a genuine element. But Brandt’s original identification held up, and he is credited as the discoverer.
Why Cobalt Took So Long to Be Recognized
Three thousand years of human use before formal discovery seems like a long time, but it makes more sense when you consider how cobalt actually behaves. The element almost never occurs in nature as a free metal. Instead, it appears locked inside complex ores that also contain arsenic, sulfur, nickel, and iron. Extracting pure cobalt from these ores requires fairly sophisticated chemical techniques that were not available until the 18th century. By contrast, metals such as gold and copper sometimes occur in native (pure) form, which is why they were identified much earlier in human history.
Additionally, the amount of cobalt needed to produce a vivid blue is tiny. A fraction of a percent of cobalt oxide in glass is enough to give it a deep blue color. Artisans did not need to isolate the metal to use it; they simply needed to know which rocks to grind up and add to their glass melt. This meant there was no practical pressure to figure out what the coloring agent actually was. The craft worked perfectly well without the chemistry.
Brandt’s achievement was, in a sense, an exercise in proving that something existed when nobody particularly needed it to exist as a separate thing. The pigment market was thriving, the miners knew which rocks to avoid, and the glassmakers knew which rocks to seek. What Brandt added was understanding: the blue was not iron, not bismuth, not copper, but something genuinely new in the catalog of metals. This was a significant intellectual achievement in an era when the very concept of a chemical element was still being defined.
Cobalt Inside You
Cobalt is not just an industrial curiosity. It is one of the trace elements essential to human life, though you need only a minuscule amount. The element’s biological importance centers on vitamin B12, also called cobalamin. The name itself reveals the connection: cobalamin is built around a single cobalt atom held in place by a ring-shaped molecular structure called a corrin. This makes vitamin B12 one of the most structurally complex small molecules produced in nature, and cobalt is its indispensable core.3PubMed Central. The requirement for cobalt in vitamin B12: A paradigm for protein metalation
Vitamin B12 is critical for red blood cell formation, neurological function, and DNA synthesis. Humans cannot make B12 themselves; it must come from dietary sources, primarily animal products like meat, fish, eggs, and dairy. The cobalt in your diet ultimately comes from the soil, where microorganisms incorporate it into B12, which then moves up the food chain. A typical adult body contains only about a milligram of cobalt, almost all of it locked in B12 molecules. You would never need cobalt supplementation on its own, but a B12 deficiency is effectively a cobalt-function deficiency.
When Cobalt Goes Wrong
While trace amounts of cobalt are essential, larger exposures can be genuinely dangerous. The most dramatic episode in cobalt toxicology occurred in the 1960s, when breweries in several countries began adding cobalt sulfate to beer as a foam stabilizer. In Minneapolis, between 1964 and 1967, twenty-eight heavy beer drinkers were admitted to a single hospital with a distinctive form of heart failure. The syndrome looked different from ordinary alcoholic heart disease: it came on suddenly, with left ventricular failure, shock, and an unusual combination of pericardial effusion and elevated red blood cell counts that pointed toward cobalt poisoning.4The American Journal of Medicine. Cobalt-beer cardiomyopathy: A clinical and pathologic study of twenty-eight cases
What made the beer cardiomyopathy cases puzzling was that the amount of cobalt in the beer, up to about 10 milligrams per day for heavy drinkers, was far less than the doses that had been used medically to treat anemia (up to 50 milligrams per day) without causing the same kind of heart damage. Researchers concluded that poor nutrition, thiamine deficiency, zinc depletion, and pre-existing alcohol damage to the heart all conspired to make these drinkers especially vulnerable to cobalt’s toxic effects. The beer-additive practice was quickly banned after the outbreaks were identified.
Occupational exposure remains a concern today, particularly in industries that produce or work with hard metals, which are alloys of tungsten carbide cemented together with cobalt. Workers who inhale cobalt-containing dust, especially when it is mixed with tungsten carbide particles, can develop an interstitial lung disease known as hard metal disease. The key finding from decades of research is that pure cobalt dust alone rarely causes this condition; the toxicity depends on an interaction between cobalt and metallic carbides that generates reactive oxygen species in lung tissue.5PubMed. Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease) This may help explain why only a fraction of exposed workers develop the disease: individuals with lower antioxidant defenses appear more susceptible.6PubMed. Experimental research into the pathogenesis of cobalt/hard metal lung disease
From Pigments to Superalloys and Catalysts
After Brandt’s discovery, cobalt spent about two centuries being valued primarily for the same thing it had always been valued for: its blue. Cobalt blue pigments and glazes remained its main commercial application through the 1800s. The 20th century, however, dramatically expanded cobalt’s industrial profile.
One of the first major new applications came in the 1930s with the development of cobalt-based catalysts for chemical synthesis. In 1938, the German chemist Otto Roelen discovered that cobalt catalysts could drive the carbonylation of ethylene to produce propanal, a reaction that emerged from research on the Fischer-Tropsch process for converting synthesis gas into liquid fuels.7Chinese Journal of Catalysis. Heterogeneous Co-based catalytic systems for alkene hydroformylation This discovery launched hydroformylation as an industrial process, and cobalt catalysts remain important in chemical manufacturing today, though many processes have shifted to rhodium-based alternatives for higher selectivity.
Cobalt also became central to high-performance magnets. Starting in the 1960s, researchers developed rare-earth cobalt alloys that produced permanent magnets far more powerful than anything previously available. These magnets, particularly samarium-cobalt types, found uses in aerospace, military electronics, and precision instruments where performance in extreme temperatures was essential.8Journal of Magnetism and Magnetic Materials. Rare earth-cobalt permanent magnets The rare-earth cobalt magnets also paved the way for the later development of neodymium-iron-boron magnets, which are now ubiquitous in consumer electronics, wind turbines, and electric vehicles. In a sense, cobalt’s contribution to magnet science helped create the technological pathway that the modern green energy transition depends on.
Superalloys represent another critical application. Jet engine turbine blades need to withstand extreme temperatures while maintaining structural integrity, and cobalt-based or cobalt-containing superalloys are among the few materials that can do this reliably. Without cobalt, modern aviation would look very different. The same goes for medical implants: cobalt-chromium alloys are widely used in hip and knee replacements because of their strength, corrosion resistance, and biocompatibility.
The Cobalt Supply Problem
Cobalt’s modern importance has created a supply chain that raises serious ethical and geopolitical concerns. The largest deposits of cobalt on land are concentrated in the Central African Copperbelt, particularly in the Democratic Republic of the Congo. These deposits formed through geological processes acting on sediments during the Neoproterozoic era, and they are among the richest cobalt sources anywhere on Earth.9Journal of African Earth Sciences. Genesis of sediment-hosted stratiform copper–cobalt deposits, central African Copperbelt The DRC currently accounts for roughly 70 percent of global cobalt mine production, a concentration of supply that has geopolitical consequences and has drawn international attention due to well-documented concerns about working conditions, including child labor in artisanal mining operations.
The search for alternative supply has led some researchers to look to the ocean floor. Ferromanganese nodules, potato-sized lumps of metal oxide that litter vast stretches of the deep seabed, contain significant concentrations of cobalt, manganese, nickel, and copper. These nodules were first discovered during the HMS Challenger oceanographic expedition of 1872 to 1876, when samples were dredged from the seafloor.10Deep Sea Research Part I: Oceanographic Research Papers. On the discovery of ferromanganese nodules in the World Ocean Whether deep-sea mining of these nodules is technically feasible, economically viable, and environmentally acceptable remains one of the most contested questions in resource policy today. Several countries and companies have secured exploration licenses for nodule-rich areas of the Pacific, but large-scale commercial extraction has not yet begun.
Cobalt-60 and the Atomic Age
The discovery of artificial radioactivity in the 20th century added yet another chapter to cobalt’s story. Cobalt-60, a radioactive isotope produced by bombarding stable cobalt-59 with neutrons in a nuclear reactor, became one of the most widely used radiation sources in the world. Its applications span two very different domains: medicine and industry.
In radiation therapy, cobalt-60 units were workhorses of cancer treatment from the 1950s through the 1980s. A cobalt-60 source produces high-energy gamma rays that can be directed at tumors, and the units were far less expensive and mechanically simpler than the linear accelerators that eventually replaced them in wealthier countries. Cobalt-60 teletherapy machines are still in use in many lower-income nations where linear accelerators are too costly to purchase and maintain. Outside medicine, cobalt-60 is used for industrial radiography, food irradiation to kill pathogens, and sterilization of medical equipment.
The dual-use nature of cobalt-60 has also raised security concerns. “Orphaned” cobalt-60 sources, meaning units that have been lost, abandoned, or stolen, pose radiation exposure risks and have been involved in several serious accidents worldwide. The most infamous occurred in Goiânia, Brazil, in 1987, when scavengers broke open an abandoned radiotherapy unit containing cesium-137 rather than cobalt-60, but similar incidents involving cobalt sources have occurred elsewhere and prompted international tracking and recovery programs.
A Metal Hiding in Plain Sight
Cobalt’s history is essentially the story of an element that was useful for millennia, feared by miners, and only formally recognized when one determined chemist decided to figure out what was actually behind the blue. Brandt’s 1735 identification set the stage, but most of what makes cobalt important today, from rechargeable batteries to superalloys to vitamin B12, was understood only in the 20th century. The element has a way of surfacing in unexpected contexts: in your bloodstream, in the pigment on a 3,400-year-old Egyptian glass bead, in the turbine of a jet engine, and in the political negotiations over deep-sea mining rights. Few elements touch as many different areas of human activity while remaining so little known to the general public.