Chemical Composition of Common Bonding Clays

 

Type of Clay Ordinary Clay Bentonite Fire Clay

Silica SiO2
53.7 61.5 45.1
Alumina (Al2O3)
25.4 22.1 33.4
Iron oxide (Fe2O3)
6.94 4.2 2.50
Calcium oxide (CaO)
0.34 1.74 1.20
Magnesium oxide (MgO)
2.04 2.27 0.94
Titanium oxide (TiO2)
0.62 0.22 1.55
Alkalis (K2O + Na2O)
3.12 1.56 0.83
Loss on ignition
7.8 5.8 14.6
Fusion Temperature oC
1390 1330 Above 1500