Cobalt "goblin", a superstitious term used for the ore of cobalt by miners. The first attempts to smelt those ores for copper or nickel failed, yielding simply powder (cobalt(II) oxide) instead. Because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic into the highly toxic and volatile arsenic oxide, adding to the notoriety of the ore. Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt circa 1735, showing it to be a previously unknown element, different from bismuth and other traditional metals. Brandt called it a new "semi-metal". He showed that compounds of cobalt metal
Cobalt(II) oxide Cobalt(II) oxide Cobalt(II) oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder. It is used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical industry for producing cobalt(II) salts. CoO crystals adopt the periclase (rock salt) structure with a lattice constant of 4.2615 Å. It is antiferromagnetic below 16 °C. Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C: Though commercially available, cobalt(II) oxide may be prepared in the laboratory by electrolyzing a solution of