type(A) type(B) type(C) sio2 67 73 63-67 al2o3 30-1 19-21 28-30 fe2o3 0.2 0.8 0.1 - 0.5 tio2 - 0.3 0.2 cao 0.2 0.56 0.7 mgo 0.4 0.3 - 0.7 0.9 -1 k2o 0.7 2 - 3.1 4.5 - 5 na2o 0.5 0.5 - 1 0.9 - 1.2 so3 0.01 - - color white to cream white to gray white to cream fired strenght 150 380 500 (kg/cm2) dry strenght 25 8 17.