Cobalt Tin Alumina Blue Spinel, an inorganic pigment, is the reaction product of high temperature calcination in which Aluminum (III) Oxide, Cobalt (II) Oxide, and Tin (IV) Oxide in varying amounts are homogeneously and ionically interdiffused to form a crystalline matrix of spinel. Its composition may include either one or both of the modifiers SiO2, or ZnO.