Synthetic Dioctahedral Montmorillonites

The study dealing with synthetic K-beidellite (Velde, 1969) is probably more valuable in the sense that longer experimental durations were performed 

The charge on the basic 2 1 fully expandable structure will be significantly lower than the 0.33 value assumed ideal (Brown, 1961). 

The solid solution (interlayering in this case) between mica and montmorillonite is gradually decreased from the montmorillonite end member and, as temperature increases, only the 30% expandable layer form persists near 400°C. 

Mg ions present in the octahedral position. The potassic, magnesian, dioctahedral montmorillonite appears to be stable up to 420°C at 2Kb pressure. 

Dioctahedral montmorillonites with Mg as an interlayer ion in the system Mg-Si-Al-f O have been synthesized at 25°C (Harder, 1972) and 80°C, 

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Figure 41. Phase diagram for the extensive variables R -R -Si combining the data for synthetic magnesian chlorites and the compositional series of natural sepiolites and palygorskites. Numbers represent the major three-phase assemblages related to sepiolite-palygorskite occurrence in sediments. Chi = chlorite M03 = trioctahedral montmorillonites M02 = dioctahedral montmorillonite Sep = sepiolite Pa = palygorskite Kaol = kaolinite T = talc.

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