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 blue Cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with alumina at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAlO. Cobalt blue is lighter and less intense than the (iron-cyanide based) pigment Prussian blue. It is extremely stable and has historically been used as a coloring agent in ceramics (especially Chinese porcelain), jewelry, and paint. Transparent glasses are tinted with the silica-based cobalt pigment smalt. Cobalt blue in impure forms had long been used in Chinese porcelain, but it was independently discovered as a pure alumina-based pigment by Louis Jacques