Vermiculite and its relation to parent materials as revealed by chemical features

Mineral chem. formulas, reported in the literature and calcd. from results of chem. analyses were treated by Q-mode factor anal. to examine the compositional variability of vermiculite [1318-00-9] and its parent micas. The 3 factors accounting principally the compositional variability were (1) Mg, (2) Al + Fe3+, and (3) Fe2+ + Mn + Ti. The solid soln. ranges of the dioctahedral (fine) and trioctahedral (coarse) vermiculites, biotites, hydromicas, and phlogopites were indicated by plotting their compns. in a triangle with the vertices represented by the 3 principal factors. Although the 2 types of vermiculites can be distinguished on the triangle, they show a continuous compositional range from 1 type to the other. This probably reflects the chem. rearrangement of the vermiculite following its formation from mica. Close chem. analogy is shown of vermiculite with phlogopite but not with biotite.