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 sulfide Cobalt sulfide Cobalt sulfide is the name for chemical compounds with a formula CoS. Well-characterized species include minerals with the formula CoS, CoS, CoS, and CoS. In general, the sulfides of cobalt are black, semiconducting, insoluble in water, and nonstoichiometric. Cobalt sulfides occur widely as minerals, comprising major sources of all cobalt compounds. Binary cobalt sulfide minerals include the cattierite (CoS) and linnaeite (CoS). CoS (see image in table) is isostructural with iron pyrite, featuring disulfide groups, i.e. CoS. Linnaeite, also rare, adopts the spinel motif. The CoS compound is known as a very rare cobaltpentlandite (the Co analogue of