Which of the following mineral is non-expanding 2 : 1 type mineral

Solution (By Examveda Team)

IIIite is the non-expanding 2 : 1 type mineral among the following given options.
Illite is a group of closely related non-expanding clay minerals. It is a secondary mineral precipitate and an example of a phyllosilicate, or layered alumino-silicate.
Its structure is a 2 : 1 sandwich of silica tetrahedron (T) - alumina octahedron (O) - silica tetrahedron (T) layers.