Silicon-aluminum order-disorder

Laves, F., and S. Hafner, 1956. Order/disorder and infrared absorption. I. (Aluminum, silicon)-distribution in feldspars. Z. Krist. 108 52. 

Ultramarine is essentially a three-dimensional aluminosilicate lattice with entrapped sodium ions and ionic sulfur groups (Fig. 32). The lattice has the sodalite structure, with a cubic unit cell dimension of ca. 0.9 nm. In synthetic ultramarine derived from china clay by calcination (see Section 3.5.3), the lattice distribution of silicon and aluminum ions is disordered. This contrasts with the ordered array in natural ultramarines. 

A new zeolite cannot be deMed solely by the symmetry difference from order or disorder of the aluminum and silicon in the framework. 

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