Palysepioles

Palygorskite (T), and sepiolite (5) are the end members of a modular series named palysepiole (pa/ygorskite -f sepiohit) polysomatic series P S [47] kalifersite is the P Si member. Falcondoite [51] and loughlinite [52] differ from sepiolite only in the composition of the O sheet in the TOT ribbons the same situation holds for yofortierite [53] and tuperssuatsiaite [54] in comparison to palygorskite. 

Because the sepiolite framework is substantially modified, intersilite is in a plesiotype relationship with the palysepiole polysomatic series. 

A description of the palysepiole polysomatic series and related structures offers the opportunity to mention the main members of the lintisite series of which the crystal stmctures are based on three building modules. One of these modules is a cut of sili-naite [57] (NaLiSi205.2H20 C2/c, a = 14.383, b = 8.334, c = 5.061 A, 13 = 96.6°), a crystal structure that shows a chess-board arrangement of channels and ribbons comparable with that of palysepioles. Modules of silinaite (S) have been used [58] as one of three modules needed to describe the modularity in the lintisite group (Figure 17-14). The other two modules are slabs (L) of the structures of lorenzenite [59]... 

The palysepiole polysomatic series PpSs (Ferraris et al. 1998) includes minerals whose structures contain one or both the types of TOT ribbons (modules) which are present in palygorskite and sepiolite these ribbons are reminiscent of the TOT modules occurring in amphiboles (Fig. 19). The two modules are ... 

Guggenheim and Eggleton (1987, 1988) described some modular 2 1 layer silicates in terms of fragments of the M (TOT) mica module, with or without interlayer cations. The modularity of these silicates originates by the inversion of part of the tetrahedral linkage. On the basis of the inversion fragments, the basic TOT layers may form either islands (e.g., stilpnomelane and zussmanite) or strips (where the octahedral sheets remains continuous as in ganophyllite and minnesotaite, or discontinuous as in the above mentioned palysepioles). 

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