Compositional and structural relationships between phengites and illites*

Necip Güven
Department of Geology, University of Illinois, Urbana, Illinois 61801, U.S.A.
* Presented at the 18th Clay Minerals Conference Oct. 19–22, 1969 under the title “the crystal structure of 2M1 phengite and its relation to the dioctahedral mica-type clay minerals”.

Summary: Dioctahedral mica-type 10 Å clay minerals are more closely related in their composition and environment to phengites than to muscovites. Structural effects of the VIR2+Si for VIAlIVAl isomorphic substitutions (R = Mg, Fe2+) along the muscovite-phengite join, as assessed from the recent crystal structure refinements of these micas, allow inferences to be made concerning the structural features in illite and its polymorphism.

Clays and Clay Minerals; November 1970 v. 18; no. 4; p. 233-235; DOI: 10.1346/CCMN.1970.0180407
© 1970, The Clay Minerals Society
Clay Minerals Society (www.clays.org)