Modular Microporous Minerals: Cancrinite-Davyne Group and C-S-H Phases

In this chapter, we illustrate and discuss two distinct groups of microporous phases: the cancrinite group and the C-S-H compounds of the tobermorite and gyrolite families. The compounds in the fi rst group present a three-dimensional purely tetrahedral framework with, apart from a single exception, Si:Al ratio equal to 1; in the mineralogical classifi cations they are included among feldspathoids and are generally “regarded …… distinct from zeolites, in part, at least, because of the presence of large volatile anions” (Coombs et al. 1998). The members of the second group are characterized by mixed frameworks built up by silicon (and aluminum) tetrahedra and calcium polyhedra. A common feature of both groups is the modular character of their frameworks, which are built up through various stacking ways of a single module (as in the minerals of the cancrinite-davyne family) and two or more modules as in the case of the C-S-H phases.