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 glass Cobalt glass Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue colored glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense glass colorant and very little is required to show a noticeable amount of color. Cobalt blue glass is also used as an optical filter in flame tests to filter out the yellow flame caused by contamination with sodium, and expand the ability to see violet and blue hues. Moderately ground cobalt glass (potassium cobalt silicate)—called "smalt"—has been historically important as a pigment in