Vermiculite from phlogopite

Forster (1961, 1963) reported a similar release and uptake of K by the mycelium of A. niger and a variety of other soil fungi when incubated with orthoclase and oligoclase. Weed et al. (1969) demonstrated that fungi weathered biotite, muscovite and phlogopite to vermiculite by acting as a sink for the K released from these minerals. Wheat plants apparently function in this manner during the alteration of biotite to vermiculite (Mortland etal., 1956). 

Vermiculite may form from the alteration of biotite or phlogopite, or of other Fe- and Mg-rich aluminosilicates, such as chlorites and hornblende in igneous or metamorphic rocks. 

Another member of the illite group is hydrous mica, in which the principal interlayer cation is K. A smectite you might encounter is montmorillonite smectites can expand by incorporating water or organics between the structural layers. Vermiculite is derived from the Latin vermiculare, which means to breed worms, and describes what appears to happen when the material is heated rapidly. Otherwise it is very similar to phlogopite mica. As you would guess, most of these minerals have complex chemical compositions. 

These experiments do not prove, but suggest the existence of a qualitative boundary separating saponites from vermiculites. This boundary cannot be found in the structural formula. If it exists, it can only be found in the distribution (ordered and disordered) of isomorphous replacements. The exact structure of saponites is still poorly known. Vermiculites are most often derived from biotite and phlogopite and could inherit the structure of the tetrahedral layers of micas. The A1 atoms in the tetrahedral layers of micas form unidimensional, ordered ensembles (linear chains of substitution Gatineau [1964] and Gatineau and Merino [1966]). 

Lashinger, J. E., 1944. Alteration of phlogopite to vermiculite. Min. Res. Lab. Johannesburg, 1 1. Leggett, G. E., and C. D. Moodie, 1963. The release of fixed ammonium from soils by sodium as affected by small amounts of potassium or ammonium. Proc. Soil Sci. Soc. Am. 27 645. Lopez-Gonsalez, J. de D., and J. Cano-Ruiz, 1959. Surface area changes of a vermiculite by acid and thermal treatment. Clays Clay Min. 6 399. 

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