Solid solution, celadonite

Natural mica compositions of the dioctahedral, potassic types have been discussed by Velde (1965b) in connection with the solid solution between muscovite and the different celadonite mica molecules. It was shown that both natural and synthetic micas formed two distinct compositional and genetic groups. The important point made in the discussion is the definition of the term mica. The most restrictive criteria as was mentioned before is the necessity for the mineral in question to have a net charge (the sum of octahedral and tetrahedral electrostatic... 

If we now consider the bulk compositions of the mixed-layered minerals which contain both expandable and non-expandable layers, two series are apparent, one between theoretical beidellite and illite and one between theoretical montmorillonite and illite (Figure 25). The intersection of the lines joining muscovite-montmorillonite and beidellite-celadonite (i.e., expandable mineral to mica), is a point which delimits, roughly, the apparent compositional fields of the two montmorillonite-illite compositional trends for the natural mixed layered minerals (Figure 26). That is, the natural minerals appear to show a compositional distribution due to solid solutions between each one of the two montmorillonite types and the two mica types—muscovite and celadonite. There is no apparent solid solution between the two highly expandable (80% montmorillonite) beidellitic and montmorillonitic end members. The point of intersection of the theoretical substitutional series beidellite = celadonite and muscovite-montmorillonite is located at about 30-40% expandable layers— 70-60% illite. This interlayering is similar to the "mineral" allevardite as defined previously. It appears that as the expandability of the mixed... 

VELDE (B.), 1972. Celadonite micas Solid solutions and stability. 

Li G, Peacor DR, Coombs DS, Kawachi Y (1997) Solid solution in the celadonite family The new... 

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