Zircon, silicon zirconium grey An inorganic pigment that is the reaction product of high temperature calcination in which zirconium oxides, silicon oxide, nickel oxide and/or chromium oxide in varying amounts are homogeneously and ionically interdiffused to form a crystalline matrix of zircon. Its composition may include any one or a combination of the modifiers cobalt oxide, manganese oxide, iron oxide, aluminium oxide, lead oxide, boron oxide and oxides and/or halides of alkali metals and alkaline earths.