Finite clusters of tetrahedra

The minerals in this class (Table 1) are dominated by polymerized (PO4) groups only in gainesite do (PO4) tetrahedra polymerize with another type of (7(1)4) group. 

In kanonerovite, Na3Mn [P30io](H20)i2, three (PO4) tetrahedra link into a [P3O10] fragment. All three (PO4) tetrahedra of this trimeric group share one vertex with the same (Mn t)6) octahedron (Fig. 7a) to form an [Mn (H20)3P30io] cluster. (Na([)6) octahedra 

The minerals in this class can be divided into two broad groups based on the (bond valence) linkage involved in the infinite chains. Minerals of this class are listed in Table 2. 

Moraesite, [Bc2(P04)(0H)](H20)4, contains chains (ribbons) of (PO4) and (Be04) tetrahedra. The (PO4) tetrahedra are four-connected and the (Be04) tetrahedra are three-connected, and the resulting [Be2(P04)(0H)] ribbons extend along the c-direction (Fig. 8a). These ribbons form a face-centered array (Fig. 8b) and are linked by hydrogen bonds involving interstitial (H2O) groups. 

The minerals in this class (Table 3) can be divided into two groups (P04)-(Be04) linkages, and (P04)-(Zn04) linkages. 

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Table 5. Phosphate minerals based on isolated tetrahedra and octahedra and finite clusters of tetrahedra and octahedra.

Structures with finite clusters of tetrahedra and octahedra... 

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