Lazurite is a silicate mineral with sulfate , sulfur and chloride . Its formula is ( Na , Ca ) 8 ( AlSiO4 ) 6 ( SO4 , S , Cl ) 2 . The main component of lapis lazuli is lazurite ( 25 % to 40 % ) , a feldspathoid silicate mineral with the formula ( Na , Ca ) 8 ( AlSiO4 ) 6 ( S , SO4 , Cl ) 1-2 .