Cobalt is a metal, and it is denoted by the chemical symbol Co. Its name has been derived from the German word kobalt, which means "goblin", which was used by the ancient cobalt ore miners. Its compounds have been used for many centuries. Use of this element is also found in the ancient Egyptian sculptures and Persian jewelry. The credit for its discovery goes to the Swedish chemist Georg Brandt. In 1735, he demonstrated that the blue color in a glass is due to the presence of cobalt, and not because of bismuth, as was believed at that time.
Usually, cobalt is not available in a metallic state, and is found in the form of minerals. The mines situated in the Democratic Republic of the Congo and Zambia, are the two main sources from which the largest quantity of this element is mined. Its principal ores are: cobaltite, glaucodot, skutterudite, erythrite, etc. All of them have a metallic luster. Generally, cobalt is mined along with nickel and chromium, and is obtained as a by-product of their extraction process.
Cobalt, in its pure form, is a hard and brittle substance in nature. Its pure metallic appearance is the same as iron and nickel. It has a high melting and boiling point. It occurs in two allotropic forms. Its atomic number is 27 and atomic mass is 58.93. It has a variable valency of 2 and 3. So far, 26 isotopes of this element have been found. Among them, Cobalt-59 is its only stable isotope, and is found naturally. There are 22 isotopes of this element, which possess radioactive properties.
Cobalt is an essential component of a number of useful alloys. Stellite is an alloy of tungsten, cobalt, and chromium, and it is used in high-speed cutting tools. It is used with iron, nickel, and some other metals in the manufacturing of Alnico, which is an alloy with high magnetic strength. It is also used as an ingredient in magnetic steel and stainless steel types. In the electroplating process, cobalt has been used extensively, as it is hard in nature and resistant towards oxidation. Salts of this element are used as pigments for the purpose of adding blue color to glass, enamels, tiles, porcelain, pottery, etc. Electrodes of Lithium-ion batteries contain a substantial amount of cobalt. Some of the compounds act as good oxidation catalysts in various chemical reactions. Cobalt-60 is a radioactive isotope of cobalt, and it's used as a source of gamma rays in radiotherapy.
Small amounts of this element act as an essential requirement for most living organisms. In human beings, it occurs necessarily as a trace nutrient. It is one of the key components of vitamin B12. It is also a nutritional substance for microorganisms like bacteria, algae, and fungi.
If the cobalt level in our body increases, then the effect is harmful, and may even lead to cancer. On direct contact with the skin, it can cause dermatitis. Cobalt in a powdered form tends to catch fire easily.