Cobalt

Cobalt is a chemical element – a substance that contains only one type of atom. Its official chemical symbol is Co and its atomic number is 27, which means that a cobalt atom has 27 protons in its nucleus. Cobalt is found in many places – in the soil, on the seafloor and in mineral deposits – but as part of a compound rather than as an element.

A transition metal

Cobalt is a transition metal – a group of 28 elements located at the centre of the periodic table of elements. Transition metals have many common properties. They are very hard, yet ductile and malleable, and they have high melting and boiling points. Cobalt is a bit different than most of the transition metals as it is naturally magnetic.

An ancient compound

Cobalt compounds have been used for centuries to add a deep blue colour to objects. Ancient Persians, Egyptians and Chinese used cobalt to colour glass beads, ceramics and glazes. They did not call it cobalt, though. People thought bismuth, one of the nine known metals at that time, was responsible for the beautiful blue colour. Swedish chemist Georg Brandt is generally credited with the discovery of cobalt as a new ‘semi-metal’ in 1735.

Chymical research and the philosophers’ stone

Thirty years prior to Georg Brandt’s published account of separating cobalt from bismuth, a young German woman had already published three books about her research using ores that contained cobalt. Dorothea Juliana Wallich was interested in chymistry (a term that covers both alchemy and chemistry). Wallich’s goal was to produce the philosophers’ stone – a substance that could turn base metals such as lead and tin into silver and gold.

Wallich’s books describe numerous chemical reactions in detail. She is credited with discovering and reporting many thermochromic effects of cobalt compounds. When heated and cooled, the compounds have colours ranging from rose, violet blue, sky blue and grass green.

Wallich became a much sought-after chymist following the publication of her books. In spite of her detailed research Wallich, like the other chymists, was unable to create the philosophers’ stone.

Named for a goblin

Wallich never used the word cobalt in her books. She used several other names – magnesia, wismuth or the secretive ‘minera’ – even though German miners had earlier coined the word cobalt to describe the ores she studied. Cobalt comes from the German word ‘kobold’ – small mountain elves or goblins. The miners thought the cruel kobold had changed the silver into worthless rocks. Smelters weren’t fond of the ores either. When heated, the ores produced poisonous fumes.

Uses for cobalt

For many centuries, cobalt was widely used as a pigment. It is best known for its strong dark-blue colour. Cobalt and mineral compounds containing cobalt are still used as pigments in blue, violet and green paints.

Cobalt – when mixed with other elements – creates alloys that do not corrode easily and are heat-resistant and wear-resistant. These alloys are used for hip and knee replacements, turbine blades and other products.

A growing use for cobalt is in lithium-ion batteries – the type of batteries used in rechargeable devices. The demand for cobalt is expected to grow as more and more people choose to drive electric vehicles.

Explore the environmental impacts in terms of CO₂ of standard vehicles vs electric vehicles in The environmental footprint of electric versus fossil cars.

Cobalt and health

Cobalt is essential to human and animal health. A cobalt atom forms the centre of the vitamin B12 chemical structure. B12 is vital for healthy red blood cell formation and neurological function. Humans get B12 from meat, dairy products, eggs and dietary supplements.

Ruminants (cows, sheep, goats and deer) obtain cobalt from the plants they eat. Bacteria in their stomachs convert cobalt to vitamin B12. In the early part of the 20th century, forested lands in the Tokoroa-Taupō-Rotorua area were cleared for grazing. Although the grass grew well, cattle and sheep became sick and often died from what became known as bush sickness. Scientists eventually discovered that the volcanic soils in this area had very low metal concentrations. Fertilisers formulated to add just a few grams of cobalt per hectare remedied the problem.