Cobalt(II) carbonate Like most transition metal carbonates, cobalt carbonate is insoluble in water, but is readily attacked by mineral acids: Cobalt carbonate is a precursor to cobalt carbonyl and various cobalt salts. It is a component of dietary supplements since cobalt is an essential element. It is a precursor to blue pottery glazes, famously in the case of Delftware. The moderately rare spherocobaltite is the natural form of cobalt carbonate, with good specimens coming especially from the Republic of Congo. "Cobaltocalcite" is a name used for a cobaltiferous calcite variety that is quite similar in habit to spherocobaltite. The compound is harmful
Cobalt with water and oxygen to brown cobalt(III) hydroxide (Co(OH)). At temperatures of 600–700 °C, CoO oxidizes to the blue cobalt(II,III) oxide (CoO), which has a spinel structure. Black cobalt(III) oxide (CoO) is also known. Cobalt oxides are antiferromagnetic at low temperature: CoO (Néel temperature 291 K) and CoO (Néel temperature: 40 K), which is analogous to magnetite (FeO), with a mixture of +2 and +3 oxidation states. The principal chalcogenides of cobalt include the black cobalt(II) sulfides, CoS, which adopts a pyrite-like structure, and cobalt(III) sulfide (CoS). Four dihalides of cobalt(II) are known: cobalt(II) fluoride (CoF, pink), cobalt(II) chloride (CoCl,