A group name for platy phyllosilicates of 2:1 layer and a layer charge of ~ -1.0 per formula unit. True micas do not show swelling capacity. Rieder et al. (1998) defines the true micas as having greater than 50% of the interlayer cations as univalent cations. The true mica group is further divided into subgroups based on the octahedral sheet being either trioctahedral or dioctahedral.
Cf., mica, brittle mica, interlayer-deficient mica, group names

See reyerite group.

A member of the palygorskite-sepiolite group with a composition of approximately Na_1.87Fe_2.14Mn_0.48Ti_0.14 (Si₈O₂₀) (OH)₂^.n(H₂O).
See palygorskite-sepiolite group

In phyllosilicates, turbostratic stacking involves highly disordered (non regular) stacking arrangements of layers where there is no registry from one layer to another, much like a stack of playing cards lying flat on each other but with no alignment of edges. Smectite minerals and halloysite commonly have turbostratic stacking.
See rotational stacking disorder