Belite Classification and Polymorphic Varieties

Type I belite crystals according to Insley (1936) were generally considered characteristic of alpha dicalcium 

Ono (1975) stated that the structure of Type I belite is skeletal instead of polysynthetically twinned. Thus, confusion, and perhaps some disagreement, in the literature exists as to the description and origin of the microstructure of Types I and II belites. The above pullout presents Ono s argument (1975), with only slight editing, in support of a largely skeletal interpretation of belite and a brief statement of polymorph origins. 

Manufacturing aspects of belite doped with barium sulfate (BaSO ), calcium tribasic phosphate [Caj(PO )30H], 

Oberste-Padtberg (1986) described an unusual belite in a Class G oil-well cement that exhibited a tendency to false set. The belite was said to be idiomor-phic, optically positive, with a 2V of more than 60 degrees, occurring as clear platy crystals with no undu-latory extinction, and extremely high concentrations of alumina and iron oxide. The present writer has never seen this type of belite and its conditions of formation appear to be largely unreported. 

Application of modern microscopical equipment, such as the transmission electron microscope, to the problem of belite microstructure appears to be aprom-ising field of research and may, as Groves (1982) stated, provide data on belite twinning types relating to the temperature at which the belite formed. 

---