A poorly defined material, possibly interstratified biotite and vermiculite or interlayer-deficient biotite.

A pseudomorph is an alteration product of a crystal that preserves the external euhedral crystal form of the precursor mineral. The pseudomorph may have a different chemical composition and/or crystal structure than the precursor crystal. The pseudomorph can result from replacement of the original structural bonds by formation of new bonds that minimize the energy toward equilibrium in response to changes in the chemical (T, P, X) environment.
Cf., alteromorph, centripetal replacement

An obsolete term for a compact, massive chlorite that resembles serpentine.

An obsolete term for poorly defined material, impure halloysite.

An obsolete term for low-Si chlorite.

An obsolete manganese oxide name, now known as cryptomelane, see hollandite. Also, a term used to describe any massive, gray to black, hard, fine-grained manganese oxide material. Often, the latter material is romanechite.
Cf., wad, romanechite

A poorly defined material, possibly a decomposition product of hornblende consisting of mica and alkali pyroxene.

A poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite or an iron-rich clinochlore.

An obsolete term for fine-grained muscovite or illite.

An obsolete term for fine-grained muscovite or illite.