 Bismuth oxychloride ( BiOCl , see figure at right ) and bismuth <unk> ( <unk> ) <unk> appear as simple anionic salts of the <unk> ( III ) cation ( BiO + ) which commonly occurs in aqueous bismuth compounds . However , in the case of BiOCl , the salt crystal forms in a structure of alternating plates of Bi , O , and Cl atoms , with each oxygen coordinating with four bismuth atoms in the adjacent plane . This mineral compound is used as a pigment and cosmetic ( see below ) . 
